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	$92.80	12.406%	$104.3128	$104.31	$104.30	$104.30
Purchase #2	$156.44	11.804%	$174.9062	$174.91	$174.90	$174.90
Purchase #3	$137.58	11.637%	$153.5902	$153.59	$153.60	$153.60
Purchase #4	$134.73	3.832%	$139.8929	$139.89	$139.90	$139.90
Purchase #5	$56.31	6.485%	$59.9617	$59.96	$59.95	$60.00
Purchase #6	$99.92	5.736%	$105.6514	$105.65	$105.65	$105.70
Purchase #7	$59.81	7.200%	$64.1163	$64.12	$64.10	$64.10
7 purchase totals =	$737.59		$802.4315	$802.43	$802.40	$802.50