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	$191.35	4.458%	$199.8804	$199.88	$199.90	$199.90
Purchase #2	$85.65	6.182%	$90.9449	$90.94	$90.95	$90.90
Purchase #3	$218.44	5.472%	$230.393	$230.39	$230.40	$230.40
Purchase #4	$55.93	9.628%	$61.3149	$61.31	$61.30	$61.30
Purchase #5	$108.27	7.123%	$115.9821	$115.98	$116.00	$116.00
Purchase #6	$250.56	9.848%	$275.2351	$275.24	$275.25	$275.20
Purchase #7	$18.60	11.631%	$20.7634	$20.76	$20.75	$20.80
7 purchase totals =	$928.80		$994.5138	$994.50	$994.55	$994.50