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	$119.46	6.424%	$127.1341	$127.13	$127.15	$127.10
Purchase #2	$198.62	10.167%	$218.8137	$218.81	$218.80	$218.80
Purchase #3	$51.55	7.721%	$55.5302	$55.53	$55.55	$55.50
Purchase #4	$16.26	11.514%	$18.1322	$18.13	$18.15	$18.10
Purchase #5	$199.29	8.553%	$216.3353	$216.34	$216.35	$216.30
Purchase #6	$161.91	5.767%	$171.2473	$171.25	$171.25	$171.20
Purchase #7	$103.28	5.849%	$109.3208	$109.32	$109.30	$109.30
7 purchase totals =	$850.37		$916.5136	$916.51	$916.55	$916.30