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	$61.45	9.730%	$67.4291	$67.43	$67.45	$67.40
Purchase #2	$200.77	13.751%	$228.3779	$228.38	$228.40	$228.40
Purchase #3	$80.93	13.564%	$91.9073	$91.91	$91.90	$91.90
Purchase #4	$242.99	3.500%	$251.4947	$251.49	$251.50	$251.50
Purchase #5	$169.72	9.110%	$185.1815	$185.18	$185.20	$185.20
Purchase #6	$35.57	12.165%	$39.8971	$39.90	$39.90	$39.90
Purchase #7	$185.43	3.405%	$191.7439	$191.74	$191.75	$191.70
7 purchase totals =	$976.86		$1,056.0315	$1,056.03	$1,056.10	$1,056.00