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	$72.96	4.537%	$76.2702	$76.27	$76.25	$76.30
Purchase #2	$55.78	6.589%	$59.4553	$59.46	$59.45	$59.50
Purchase #3	$186.75	7.265%	$200.3174	$200.32	$200.30	$200.30
Purchase #4	$228.28	11.254%	$253.9706	$253.97	$253.95	$254.00
Purchase #5	$144.48	6.449%	$153.7975	$153.80	$153.80	$153.80
Purchase #6	$90.70	9.220%	$99.0625	$99.06	$99.05	$99.10
Purchase #7	$172.75	12.161%	$193.7581	$193.76	$193.75	$193.80
7 purchase totals =	$951.70		$1,036.6316	$1,036.64	$1,036.55	$1,036.80