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	$89.44	11.126%	$99.3911	$99.39	$99.40	$99.40
Purchase #2	$211.50	4.164%	$220.3069	$220.31	$220.30	$220.30
Purchase #3	$124.81	5.231%	$131.3388	$131.34	$131.35	$131.30
Purchase #4	$135.82	9.313%	$148.4689	$148.47	$148.45	$148.50
Purchase #5	$88.40	9.741%	$97.011	$97.01	$97.00	$97.00
Purchase #6	$203.92	13.240%	$230.919	$230.92	$230.90	$230.90
Purchase #7	$139.71	5.239%	$147.0294	$147.03	$147.05	$147.00
7 purchase totals =	$993.60		$1,074.4651	$1,074.47	$1,074.45	$1,074.40