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	$82.44	8.725%	$89.6329	$89.63	$89.65	$89.60
Purchase #2	$176.31	5.753%	$186.4531	$186.45	$186.45	$186.50
Purchase #3	$153.85	11.441%	$171.452	$171.45	$171.45	$171.50
Purchase #4	$94.69	8.732%	$102.9583	$102.96	$102.95	$103.00
Purchase #5	$22.52	5.416%	$23.7397	$23.74	$23.75	$23.70
Purchase #6	$82.46	11.518%	$91.9577	$91.96	$91.95	$92.00
Purchase #7	$65.48	9.693%	$71.827	$71.83	$71.85	$71.80
7 purchase totals =	$677.75		$738.0207	$738.02	$738.05	$738.10