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	$50.57	4.501%	$52.8462	$52.85	$52.85	$52.80
Purchase #2	$122.41	4.865%	$128.3652	$128.37	$128.35	$128.40
Purchase #3	$249.88	10.102%	$275.1229	$275.12	$275.10	$275.10
Purchase #4	$58.39	13.230%	$66.115	$66.12	$66.10	$66.10
Purchase #5	$228.56	8.643%	$248.3144	$248.31	$248.30	$248.30
Purchase #6	$77.70	7.715%	$83.6946	$83.69	$83.70	$83.70
Purchase #7	$191.84	4.663%	$200.7855	$200.79	$200.80	$200.80
7 purchase totals =	$979.35		$1,055.2438	$1,055.25	$1,055.20	$1,055.20