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	$119.42	6.258%	$126.8933	$126.89	$126.90	$126.90
Purchase #2	$221.54	12.203%	$248.5745	$248.57	$248.55	$248.60
Purchase #3	$165.81	11.601%	$185.0456	$185.05	$185.05	$185.00
Purchase #4	$191.65	12.547%	$215.6963	$215.70	$215.70	$215.70
Purchase #5	$180.72	6.125%	$191.7891	$191.79	$191.80	$191.80
Purchase #6	$25.30	12.736%	$28.5222	$28.52	$28.50	$28.50
Purchase #7	$20.41	8.383%	$22.121	$22.12	$22.10	$22.10
7 purchase totals =	$924.85		$1,018.6420	$1,018.64	$1,018.60	$1,018.60