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	$42.91	10.739%	$47.5181	$47.52	$47.50	$47.50
Purchase #2	$65.39	7.145%	$70.0621	$70.06	$70.05	$70.10
Purchase #3	$148.76	8.749%	$161.775	$161.78	$161.80	$161.80
Purchase #4	$73.42	9.145%	$80.1343	$80.13	$80.15	$80.10
Purchase #5	$174.46	12.663%	$196.5519	$196.55	$196.55	$196.60
Purchase #6	$239.30	7.313%	$256.8	$256.80	$256.80	$256.80
Purchase #7	$240.85	6.175%	$255.7225	$255.72	$255.70	$255.70
7 purchase totals =	$985.09		$1,068.5639	$1,068.56	$1,068.55	$1,068.60