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	$191.44	6.479%	$203.8434	$203.84	$203.85	$203.80
Purchase #2	$141.50	8.743%	$153.8713	$153.87	$153.85	$153.90
Purchase #3	$78.89	13.386%	$89.4502	$89.45	$89.45	$89.50
Purchase #4	$231.33	13.448%	$262.4393	$262.44	$262.45	$262.40
Purchase #5	$247.63	6.333%	$263.3124	$263.31	$263.30	$263.30
Purchase #6	$243.87	4.387%	$254.5686	$254.57	$254.55	$254.60
Purchase #7	$64.56	3.136%	$66.5846	$66.58	$66.60	$66.60
7 purchase totals =	$1,199.22		$1,294.0698	$1,294.06	$1,294.05	$1,294.10