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	$128.88	12.580%	$145.0931	$145.09	$145.10	$145.10
Purchase #2	$246.88	8.353%	$267.5019	$267.50	$267.50	$267.50
Purchase #3	$234.31	6.669%	$249.9361	$249.94	$249.95	$249.90
Purchase #4	$155.76	11.384%	$173.4917	$173.49	$173.50	$173.50
Purchase #5	$238.62	10.550%	$263.7944	$263.79	$263.80	$263.80
Purchase #6	$50.54	11.427%	$56.3152	$56.32	$56.30	$56.30
Purchase #7	$37.37	6.648%	$39.8544	$39.85	$39.85	$39.90
7 purchase totals =	$1,092.36		$1,195.9868	$1,195.98	$1,196.00	$1,196.00