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	$206.34	6.825%	$220.4227	$220.42	$220.40	$220.40
Purchase #2	$230.75	9.764%	$253.2804	$253.28	$253.30	$253.30
Purchase #3	$188.73	4.288%	$196.8227	$196.82	$196.80	$196.80
Purchase #4	$7.34	6.848%	$7.8426	$7.84	$7.85	$7.80
Purchase #5	$150.84	6.833%	$161.1469	$161.15	$161.15	$161.10
Purchase #6	$139.83	5.136%	$147.0117	$147.01	$147.00	$147.00
Purchase #7	$153.96	7.140%	$164.9527	$164.95	$164.95	$165.00
7 purchase totals =	$1,077.79		$1,151.4797	$1,151.47	$1,151.45	$1,151.40