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	$179.95	11.131%	$199.9802	$199.98	$200.00	$200.00
Purchase #2	$141.39	6.359%	$150.381	$150.38	$150.40	$150.40
Purchase #3	$245.88	12.172%	$275.8085	$275.81	$275.80	$275.80
Purchase #4	$182.88	6.793%	$195.303	$195.30	$195.30	$195.30
Purchase #5	$37.62	13.258%	$42.6077	$42.61	$42.60	$42.60
Purchase #6	$161.59	5.764%	$170.904	$170.90	$170.90	$170.90
Purchase #7	$84.81	5.155%	$89.182	$89.18	$89.20	$89.20
7 purchase totals =	$1,034.12		$1,124.1664	$1,124.16	$1,124.20	$1,124.20