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	$77.42	13.686%	$88.0157	$88.02	$88.00	$88.00
Purchase #2	$146.90	6.572%	$156.5543	$156.55	$156.55	$156.60
Purchase #3	$115.42	13.651%	$131.176	$131.18	$131.20	$131.20
Purchase #4	$56.30	9.159%	$61.4565	$61.46	$61.45	$61.50
Purchase #5	$157.26	9.350%	$171.9638	$171.96	$171.95	$172.00
Purchase #6	$154.35	11.432%	$171.9953	$172.00	$172.00	$172.00
Purchase #7	$138.35	13.384%	$156.8668	$156.87	$156.85	$156.90
7 purchase totals =	$846.00		$938.0284	$938.04	$938.00	$938.20