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	$83.89	11.260%	$93.336	$93.34	$93.35	$93.30
Purchase #2	$133.48	13.501%	$151.5011	$151.50	$151.50	$151.50
Purchase #3	$53.29	8.621%	$57.8841	$57.88	$57.90	$57.90
Purchase #4	$95.73	4.656%	$100.1872	$100.19	$100.20	$100.20
Purchase #5	$85.68	4.523%	$89.5553	$89.56	$89.55	$89.60
Purchase #6	$119.34	7.689%	$128.5161	$128.52	$128.50	$128.50
Purchase #7	$57.60	7.334%	$61.8244	$61.82	$61.80	$61.80
7 purchase totals =	$629.01		$682.8042	$682.81	$682.80	$682.80