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	$129.82	10.506%	$143.4589	$143.46	$143.45	$143.50
Purchase #2	$167.31	13.306%	$189.5723	$189.57	$189.55	$189.60
Purchase #3	$82.46	7.279%	$88.4623	$88.46	$88.45	$88.50
Purchase #4	$40.27	8.226%	$43.5826	$43.58	$43.60	$43.60
Purchase #5	$228.31	6.721%	$243.6547	$243.65	$243.65	$243.70
Purchase #6	$242.41	6.805%	$258.906	$258.91	$258.90	$258.90
Purchase #7	$212.73	5.827%	$225.1258	$225.13	$225.15	$225.10
7 purchase totals =	$1,103.31		$1,192.7626	$1,192.76	$1,192.75	$1,192.90