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	$197.80	10.852%	$219.2653	$219.27	$219.25	$219.30
Purchase #2	$99.59	4.468%	$104.0397	$104.04	$104.05	$104.00
Purchase #3	$131.88	12.482%	$148.3413	$148.34	$148.35	$148.30
Purchase #4	$100.99	5.449%	$106.4929	$106.49	$106.50	$106.50
Purchase #5	$171.45	5.312%	$180.5574	$180.56	$180.55	$180.60
Purchase #6	$200.82	10.292%	$221.4884	$221.49	$221.50	$221.50
Purchase #7	$53.91	13.487%	$61.1808	$61.18	$61.20	$61.20
7 purchase totals =	$956.44		$1,041.3658	$1,041.37	$1,041.40	$1,041.40