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	$196.37	10.481%	$216.9515	$216.95	$216.95	$217.00
Purchase #2	$212.69	4.215%	$221.6549	$221.65	$221.65	$221.70
Purchase #3	$73.62	12.837%	$83.0706	$83.07	$83.05	$83.10
Purchase #4	$105.56	3.685%	$109.4499	$109.45	$109.45	$109.40
Purchase #5	$72.48	11.130%	$80.547	$80.55	$80.55	$80.50
Purchase #6	$33.89	3.558%	$35.0958	$35.10	$35.10	$35.10
Purchase #7	$60.44	8.437%	$65.5393	$65.54	$65.55	$65.50
7 purchase totals =	$755.05		$812.3090	$812.31	$812.30	$812.30