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	$149.36	13.230%	$169.1203	$169.12	$169.10	$169.10
Purchase #2	$102.66	8.667%	$111.5575	$111.56	$111.55	$111.60
Purchase #3	$108.53	9.511%	$118.8523	$118.85	$118.85	$118.90
Purchase #4	$225.40	4.541%	$235.6354	$235.64	$235.65	$235.60
Purchase #5	$189.30	7.481%	$203.4615	$203.46	$203.45	$203.50
Purchase #6	$94.59	11.413%	$105.3856	$105.39	$105.40	$105.40
Purchase #7	$35.89	13.290%	$40.6598	$40.66	$40.65	$40.70
7 purchase totals =	$905.73		$984.6724	$984.68	$984.65	$984.80