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	$98.28	12.504%	$110.5689	$110.57	$110.55	$110.60
Purchase #2	$87.97	9.854%	$96.6386	$96.64	$96.65	$96.60
Purchase #3	$116.56	12.865%	$131.5554	$131.56	$131.55	$131.60
Purchase #4	$106.57	9.844%	$117.0608	$117.06	$117.05	$117.10
Purchase #5	$35.91	6.115%	$38.1059	$38.11	$38.10	$38.10
Purchase #6	$88.93	11.490%	$99.1481	$99.15	$99.15	$99.10
Purchase #7	$34.92	7.519%	$37.5456	$37.55	$37.55	$37.50
7 purchase totals =	$569.14		$630.6233	$630.64	$630.60	$630.60