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	$98.56	7.313%	$105.7677	$105.77	$105.75	$105.80
Purchase #2	$157.43	13.278%	$178.3336	$178.33	$178.35	$178.30
Purchase #3	$106.77	11.519%	$119.0688	$119.07	$119.05	$119.10
Purchase #4	$33.79	6.118%	$35.8573	$35.86	$35.85	$35.90
Purchase #5	$85.67	11.305%	$95.355	$95.36	$95.35	$95.40
Purchase #6	$87.93	13.768%	$100.0362	$100.04	$100.05	$100.00
Purchase #7	$89.50	7.384%	$96.1087	$96.11	$96.10	$96.10
7 purchase totals =	$659.65		$730.5273	$730.54	$730.50	$730.60