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	$30.38	9.414%	$33.24	$33.24	$33.25	$33.20
Purchase #2	$191.54	3.125%	$197.5256	$197.53	$197.55	$197.50
Purchase #3	$136.70	10.179%	$150.6147	$150.61	$150.60	$150.60
Purchase #4	$223.91	8.757%	$243.5178	$243.52	$243.50	$243.50
Purchase #5	$77.28	10.655%	$85.5142	$85.51	$85.50	$85.50
Purchase #6	$6.27	13.270%	$7.102	$7.10	$7.10	$7.10
Purchase #7	$190.26	5.491%	$200.7072	$200.71	$200.70	$200.70
7 purchase totals =	$856.34		$918.2215	$918.22	$918.20	$918.10