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	$95.73	3.481%	$99.0624	$99.06	$99.05	$99.10
Purchase #2	$145.85	13.235%	$165.1532	$165.15	$165.15	$165.20
Purchase #3	$46.81	8.363%	$50.7247	$50.72	$50.70	$50.70
Purchase #4	$187.44	13.732%	$213.1793	$213.18	$213.20	$213.20
Purchase #5	$151.37	4.723%	$158.5192	$158.52	$158.50	$158.50
Purchase #6	$130.72	13.874%	$148.8561	$148.86	$148.85	$148.90
Purchase #7	$204.58	3.589%	$211.9224	$211.92	$211.90	$211.90
7 purchase totals =	$962.50		$1,047.4173	$1,047.41	$1,047.35	$1,047.50