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	$144.91	7.621%	$155.9536	$155.95	$155.95	$156.00
Purchase #2	$201.25	11.255%	$223.9007	$223.90	$223.90	$223.90
Purchase #3	$47.67	10.126%	$52.4971	$52.50	$52.50	$52.50
Purchase #4	$48.77	9.505%	$53.4056	$53.41	$53.40	$53.40
Purchase #5	$72.86	13.221%	$82.4928	$82.49	$82.50	$82.50
Purchase #6	$59.33	9.429%	$64.9242	$64.92	$64.90	$64.90
Purchase #7	$81.27	5.179%	$85.479	$85.48	$85.50	$85.50
7 purchase totals =	$656.06		$718.6530	$718.65	$718.65	$718.70