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	$215.50	3.115%	$222.2128	$222.21	$222.20	$222.20
Purchase #2	$72.79	4.821%	$76.2992	$76.30	$76.30	$76.30
Purchase #3	$158.54	4.425%	$165.5554	$165.56	$165.55	$165.60
Purchase #4	$61.30	5.826%	$64.8713	$64.87	$64.85	$64.90
Purchase #5	$129.87	3.167%	$133.983	$133.98	$134.00	$134.00
Purchase #6	$196.86	3.352%	$203.4587	$203.46	$203.45	$203.50
Purchase #7	$30.45	11.367%	$33.9113	$33.91	$33.90	$33.90
7 purchase totals =	$865.31		$900.2917	$900.29	$900.25	$900.40