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	$170.71	4.384%	$178.1939	$178.19	$178.20	$178.20
Purchase #2	$64.30	12.412%	$72.2809	$72.28	$72.30	$72.30
Purchase #3	$200.56	12.148%	$224.924	$224.92	$224.90	$224.90
Purchase #4	$212.75	7.596%	$228.9105	$228.91	$228.90	$228.90
Purchase #5	$184.43	13.154%	$208.6899	$208.69	$208.70	$208.70
Purchase #6	$101.53	4.325%	$105.9212	$105.92	$105.90	$105.90
Purchase #7	$27.89	5.108%	$29.3146	$29.31	$29.30	$29.30
7 purchase totals =	$962.17		$1,048.2350	$1,048.22	$1,048.20	$1,048.20