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	$130.92	4.816%	$137.2251	$137.23	$137.25	$137.20
Purchase #2	$50.53	4.843%	$52.9772	$52.98	$53.00	$53.00
Purchase #3	$186.53	12.353%	$209.5721	$209.57	$209.55	$209.60
Purchase #4	$58.62	5.510%	$61.85	$61.85	$61.85	$61.90
Purchase #5	$157.40	9.142%	$171.7895	$171.79	$171.80	$171.80
Purchase #6	$208.38	10.643%	$230.5579	$230.56	$230.55	$230.60
Purchase #7	$175.71	6.589%	$187.2875	$187.29	$187.30	$187.30
7 purchase totals =	$968.09		$1,051.2593	$1,051.27	$1,051.30	$1,051.40