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	$210.34	12.497%	$236.6262	$236.63	$236.65	$236.60
Purchase #2	$100.56	6.349%	$106.9446	$106.94	$106.95	$106.90
Purchase #3	$51.87	10.522%	$57.3278	$57.33	$57.35	$57.30
Purchase #4	$79.93	12.193%	$89.6759	$89.68	$89.70	$89.70
Purchase #5	$187.85	6.111%	$199.3295	$199.33	$199.35	$199.30
Purchase #6	$169.59	11.610%	$189.2794	$189.28	$189.30	$189.30
Purchase #7	$98.45	13.548%	$111.788	$111.79	$111.80	$111.80
7 purchase totals =	$898.59		$990.9714	$990.98	$991.10	$990.90