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	$11.52	7.110%	$12.3391	$12.34	$12.35	$12.30
Purchase #2	$76.63	6.489%	$81.6025	$81.60	$81.60	$81.60
Purchase #3	$189.91	11.413%	$211.5844	$211.58	$211.60	$211.60
Purchase #4	$85.69	13.111%	$96.9248	$96.92	$96.90	$96.90
Purchase #5	$93.67	7.272%	$100.4817	$100.48	$100.50	$100.50
Purchase #6	$130.97	13.677%	$148.8828	$148.88	$148.90	$148.90
Purchase #7	$184.70	8.669%	$200.7116	$200.71	$200.70	$200.70
7 purchase totals =	$773.09		$852.5269	$852.51	$852.55	$852.50