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	$149.36	8.811%	$162.5201	$162.52	$162.50	$162.50
Purchase #2	$101.96	9.186%	$111.326	$111.33	$111.35	$111.30
Purchase #3	$145.47	11.119%	$161.6448	$161.64	$161.65	$161.60
Purchase #4	$56.81	3.590%	$58.8495	$58.85	$58.85	$58.80
Purchase #5	$88.46	13.121%	$100.0668	$100.07	$100.05	$100.10
Purchase #6	$136.34	11.692%	$152.2809	$152.28	$152.30	$152.30
Purchase #7	$79.90	13.165%	$90.4188	$90.42	$90.40	$90.40
7 purchase totals =	$758.30		$837.1069	$837.11	$837.10	$837.00