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	$102.63	8.621%	$111.4777	$111.48	$111.50	$111.50
Purchase #2	$61.63	7.612%	$66.3213	$66.32	$66.30	$66.30
Purchase #3	$179.76	11.762%	$200.9034	$200.90	$200.90	$200.90
Purchase #4	$220.35	12.699%	$248.3322	$248.33	$248.35	$248.30
Purchase #5	$48.61	7.359%	$52.1872	$52.19	$52.20	$52.20
Purchase #6	$250.94	6.662%	$267.6576	$267.66	$267.65	$267.70
Purchase #7	$147.67	12.790%	$166.557	$166.56	$166.55	$166.60
7 purchase totals =	$1,011.59		$1,113.4364	$1,113.44	$1,113.45	$1,113.50