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	$98.43	7.215%	$105.5317	$105.53	$105.55	$105.50
Purchase #2	$226.25	13.471%	$256.7281	$256.73	$256.75	$256.70
Purchase #3	$180.63	4.491%	$188.7421	$188.74	$188.75	$188.70
Purchase #4	$50.30	11.370%	$56.0191	$56.02	$56.00	$56.00
Purchase #5	$37.97	4.486%	$39.6733	$39.67	$39.65	$39.70
Purchase #6	$206.92	7.533%	$222.5073	$222.51	$222.50	$222.50
Purchase #7	$31.61	11.617%	$35.2821	$35.28	$35.30	$35.30
7 purchase totals =	$832.11		$904.4837	$904.48	$904.50	$904.40