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	$37.34	8.743%	$40.6046	$40.60	$40.60	$40.60
Purchase #2	$225.88	8.772%	$245.6942	$245.69	$245.70	$245.70
Purchase #3	$209.79	6.297%	$223.0005	$223.00	$223.00	$223.00
Purchase #4	$167.90	4.329%	$175.1684	$175.17	$175.15	$175.20
Purchase #5	$162.60	11.209%	$180.8258	$180.83	$180.85	$180.80
Purchase #6	$156.57	5.873%	$165.7654	$165.77	$165.75	$165.80
Purchase #7	$233.45	6.436%	$248.4748	$248.47	$248.45	$248.50
7 purchase totals =	$1,193.53		$1,279.5337	$1,279.53	$1,279.50	$1,279.60