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	$90.89	5.102%	$95.5272	$95.53	$95.55	$95.50
Purchase #2	$77.69	9.467%	$85.0449	$85.04	$85.05	$85.00
Purchase #3	$179.30	3.776%	$186.0704	$186.07	$186.05	$186.10
Purchase #4	$82.46	8.842%	$89.7511	$89.75	$89.75	$89.80
Purchase #5	$73.82	12.286%	$82.8895	$82.89	$82.90	$82.90
Purchase #6	$57.29	9.514%	$62.7406	$62.74	$62.75	$62.70
Purchase #7	$133.31	13.408%	$151.1842	$151.18	$151.20	$151.20
7 purchase totals =	$694.76		$753.2079	$753.20	$753.25	$753.20