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	$168.62	13.718%	$191.7513	$191.75	$191.75	$191.80
Purchase #2	$212.51	13.849%	$241.9405	$241.94	$241.95	$241.90
Purchase #3	$228.29	7.720%	$245.914	$245.91	$245.90	$245.90
Purchase #4	$157.35	5.434%	$165.9004	$165.90	$165.90	$165.90
Purchase #5	$28.26	10.680%	$31.2782	$31.28	$31.30	$31.30
Purchase #6	$204.96	5.132%	$215.4785	$215.48	$215.50	$215.50
Purchase #7	$9.89	11.515%	$11.0288	$11.03	$11.05	$11.00
7 purchase totals =	$1,009.88		$1,103.2917	$1,103.29	$1,103.35	$1,103.30