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	$180.84	4.423%	$188.8386	$188.84	$188.85	$188.80
Purchase #2	$55.56	12.468%	$62.4872	$62.49	$62.50	$62.50
Purchase #3	$120.83	7.607%	$130.0215	$130.02	$130.00	$130.00
Purchase #4	$70.50	10.348%	$77.7953	$77.80	$77.80	$77.80
Purchase #5	$87.59	12.497%	$98.5361	$98.54	$98.55	$98.50
Purchase #6	$145.90	8.636%	$158.4999	$158.50	$158.50	$158.50
Purchase #7	$16.62	13.279%	$18.827	$18.83	$18.85	$18.80
7 purchase totals =	$677.84		$735.0056	$735.02	$735.05	$734.90