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	$172.32	6.747%	$183.9464	$183.95	$183.95	$183.90
Purchase #2	$58.84	10.277%	$64.887	$64.89	$64.90	$64.90
Purchase #3	$129.33	10.296%	$142.6458	$142.65	$142.65	$142.60
Purchase #4	$61.94	8.669%	$67.3096	$67.31	$67.30	$67.30
Purchase #5	$249.98	11.764%	$279.3876	$279.39	$279.40	$279.40
Purchase #6	$139.35	9.429%	$152.4893	$152.49	$152.50	$152.50
Purchase #7	$80.75	5.469%	$85.1662	$85.17	$85.15	$85.20
7 purchase totals =	$892.51		$975.8319	$975.85	$975.85	$975.80