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	$230.30	5.704%	$243.4363	$243.44	$243.45	$243.40
Purchase #2	$71.46	4.707%	$74.8236	$74.82	$74.80	$74.80
Purchase #3	$240.74	7.761%	$259.4238	$259.42	$259.40	$259.40
Purchase #4	$11.82	7.510%	$12.7077	$12.71	$12.70	$12.70
Purchase #5	$152.50	5.326%	$160.6222	$160.62	$160.60	$160.60
Purchase #6	$162.89	6.810%	$173.9828	$173.98	$174.00	$174.00
Purchase #7	$196.43	13.144%	$222.2488	$222.25	$222.25	$222.20
7 purchase totals =	$1,066.14		$1,147.2452	$1,147.24	$1,147.20	$1,147.10