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	$85.33	3.173%	$88.0375	$88.04	$88.05	$88.00
Purchase #2	$143.53	4.786%	$150.3993	$150.40	$150.40	$150.40
Purchase #3	$55.32	8.223%	$59.869	$59.87	$59.85	$59.90
Purchase #4	$190.64	5.150%	$200.458	$200.46	$200.45	$200.50
Purchase #5	$175.47	10.517%	$193.9242	$193.92	$193.90	$193.90
Purchase #6	$200.33	5.513%	$211.3742	$211.37	$211.35	$211.40
Purchase #7	$244.66	13.240%	$277.053	$277.05	$277.05	$277.10
7 purchase totals =	$1,095.28		$1,181.1152	$1,181.11	$1,181.05	$1,181.20