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	$197.56	9.525%	$216.3776	$216.38	$216.40	$216.40
Purchase #2	$149.89	11.605%	$167.2847	$167.28	$167.30	$167.30
Purchase #3	$93.95	6.125%	$99.7044	$99.70	$99.70	$99.70
Purchase #4	$46.88	12.451%	$52.717	$52.72	$52.70	$52.70
Purchase #5	$222.48	4.174%	$231.7663	$231.77	$231.75	$231.80
Purchase #6	$85.41	12.627%	$96.1947	$96.19	$96.20	$96.20
Purchase #7	$185.37	10.508%	$204.8487	$204.85	$204.85	$204.80
7 purchase totals =	$981.54		$1,068.8934	$1,068.89	$1,068.90	$1,068.90