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	$172.72	7.467%	$185.617	$185.62	$185.60	$185.60
Purchase #2	$188.91	3.361%	$195.2593	$195.26	$195.25	$195.30
Purchase #3	$101.60	3.673%	$105.3318	$105.33	$105.35	$105.30
Purchase #4	$119.29	10.222%	$131.4838	$131.48	$131.50	$131.50
Purchase #5	$84.68	8.541%	$91.9125	$91.91	$91.90	$91.90
Purchase #6	$233.67	3.820%	$242.5962	$242.60	$242.60	$242.60
Purchase #7	$149.67	11.527%	$166.9225	$166.92	$166.90	$166.90
7 purchase totals =	$1,050.54		$1,119.1231	$1,119.12	$1,119.10	$1,119.10