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	$154.29	7.284%	$165.5285	$165.53	$165.55	$165.50
Purchase #2	$227.89	4.462%	$238.0585	$238.06	$238.05	$238.10
Purchase #3	$37.75	6.469%	$40.192	$40.19	$40.20	$40.20
Purchase #4	$89.41	10.740%	$99.0126	$99.01	$99.00	$99.00
Purchase #5	$141.45	4.732%	$148.1434	$148.14	$148.15	$148.10
Purchase #6	$143.94	6.563%	$153.3868	$153.39	$153.40	$153.40
Purchase #7	$33.48	11.604%	$37.365	$37.37	$37.35	$37.40
7 purchase totals =	$828.21		$881.6868	$881.69	$881.70	$881.70