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	$248.73	10.796%	$275.5829	$275.58	$275.60	$275.60
Purchase #2	$149.92	6.156%	$159.1491	$159.15	$159.15	$159.10
Purchase #3	$64.96	11.269%	$72.2803	$72.28	$72.30	$72.30
Purchase #4	$188.44	10.421%	$208.0773	$208.08	$208.10	$208.10
Purchase #5	$74.31	6.186%	$78.9068	$78.91	$78.90	$78.90
Purchase #6	$158.89	7.436%	$170.7051	$170.71	$170.70	$170.70
Purchase #7	$106.77	6.205%	$113.3951	$113.40	$113.40	$113.40
7 purchase totals =	$992.02		$1,078.0966	$1,078.11	$1,078.15	$1,078.10