Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$174.55	12.679%	$196.6812	$196.68	$196.70	$196.70
Purchase #2	$137.30	8.400%	$148.8332	$148.83	$148.85	$148.80
Purchase #3	$187.81	4.747%	$196.7253	$196.73	$196.75	$196.70
Purchase #4	$94.27	13.244%	$106.7551	$106.76	$106.75	$106.80
Purchase #5	$117.51	10.342%	$129.6629	$129.66	$129.65	$129.70
Purchase #6	$199.38	6.726%	$212.7903	$212.79	$212.80	$212.80
Purchase #7	$219.85	10.699%	$243.3718	$243.37	$243.35	$243.40
7 purchase totals =	$1,130.67		$1,234.8198	$1,234.82	$1,234.85	$1,234.90