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	$189.68	3.449%	$196.2221	$196.22	$196.20	$196.20
Purchase #2	$192.47	6.721%	$205.4059	$205.41	$205.40	$205.40
Purchase #3	$249.44	10.472%	$275.5614	$275.56	$275.55	$275.60
Purchase #4	$140.65	10.777%	$155.8079	$155.81	$155.80	$155.80
Purchase #5	$37.57	10.366%	$41.4645	$41.46	$41.45	$41.50
Purchase #6	$149.60	5.550%	$157.9028	$157.90	$157.90	$157.90
Purchase #7	$131.92	11.371%	$146.9206	$146.92	$146.90	$146.90
7 purchase totals =	$1,091.33		$1,179.2852	$1,179.28	$1,179.20	$1,179.30