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	$141.89	4.632%	$148.4623	$148.46	$148.45	$148.50
Purchase #2	$174.61	12.331%	$196.1412	$196.14	$196.15	$196.10
Purchase #3	$93.45	7.360%	$100.3279	$100.33	$100.35	$100.30
Purchase #4	$56.48	8.470%	$61.2639	$61.26	$61.25	$61.30
Purchase #5	$127.76	6.165%	$135.6364	$135.64	$135.65	$135.60
Purchase #6	$86.46	6.167%	$91.792	$91.79	$91.80	$91.80
Purchase #7	$33.91	8.398%	$36.7578	$36.76	$36.75	$36.80
7 purchase totals =	$714.56		$770.3815	$770.38	$770.40	$770.40