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	$113.47	12.850%	$128.0509	$128.05	$128.05	$128.10
Purchase #2	$48.42	4.461%	$50.58	$50.58	$50.60	$50.60
Purchase #3	$53.85	7.731%	$58.0131	$58.01	$58.00	$58.00
Purchase #4	$204.29	8.745%	$222.1552	$222.16	$222.15	$222.20
Purchase #5	$83.98	7.824%	$90.5506	$90.55	$90.55	$90.60
Purchase #6	$99.52	8.814%	$108.2917	$108.29	$108.30	$108.30
Purchase #7	$89.53	12.707%	$100.9066	$100.91	$100.90	$100.90
7 purchase totals =	$693.06		$758.5481	$758.55	$758.55	$758.70