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	$210.66	7.498%	$226.4553	$226.46	$226.45	$226.50
Purchase #2	$81.59	4.697%	$85.4223	$85.42	$85.40	$85.40
Purchase #3	$128.26	11.674%	$143.2331	$143.23	$143.25	$143.20
Purchase #4	$57.58	12.446%	$64.7464	$64.75	$64.75	$64.70
Purchase #5	$83.40	7.816%	$89.9185	$89.92	$89.90	$89.90
Purchase #6	$223.81	7.759%	$241.1754	$241.18	$241.20	$241.20
Purchase #7	$7.73	10.248%	$8.5222	$8.52	$8.50	$8.50
7 purchase totals =	$793.03		$859.4732	$859.48	$859.45	$859.40