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	$106.45	4.185%	$110.9049	$110.90	$110.90	$110.90
Purchase #2	$43.63	4.862%	$45.7513	$45.75	$45.75	$45.80
Purchase #3	$18.50	12.756%	$20.8599	$20.86	$20.85	$20.90
Purchase #4	$166.72	13.213%	$188.7487	$188.75	$188.75	$188.70
Purchase #5	$71.94	7.644%	$77.4391	$77.44	$77.45	$77.40
Purchase #6	$128.74	8.794%	$140.0614	$140.06	$140.05	$140.10
Purchase #7	$78.75	5.772%	$83.2955	$83.30	$83.30	$83.30
7 purchase totals =	$614.73		$667.0608	$667.06	$667.05	$667.10