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	$103.56	7.824%	$111.6625	$111.66	$111.65	$111.70
Purchase #2	$219.42	10.621%	$242.7246	$242.72	$242.70	$242.70
Purchase #3	$77.55	3.207%	$80.037	$80.04	$80.05	$80.00
Purchase #4	$166.62	9.505%	$182.4572	$182.46	$182.45	$182.50
Purchase #5	$238.77	3.675%	$247.5448	$247.54	$247.55	$247.50
Purchase #6	$245.54	11.853%	$274.6439	$274.64	$274.65	$274.60
Purchase #7	$58.47	12.461%	$65.7559	$65.76	$65.75	$65.80
7 purchase totals =	$1,109.93		$1,204.8259	$1,204.82	$1,204.80	$1,204.80