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	$185.43	6.140%	$196.8154	$196.82	$196.80	$196.80
Purchase #2	$159.30	4.693%	$166.7759	$166.78	$166.80	$166.80
Purchase #3	$188.70	11.762%	$210.8949	$210.89	$210.90	$210.90
Purchase #4	$206.39	13.399%	$234.0442	$234.04	$234.05	$234.00
Purchase #5	$119.30	11.563%	$133.0947	$133.09	$133.10	$133.10
Purchase #6	$161.40	4.784%	$169.1214	$169.12	$169.10	$169.10
Purchase #7	$78.32	5.613%	$82.7161	$82.72	$82.70	$82.70
7 purchase totals =	$1,098.84		$1,193.4626	$1,193.46	$1,193.45	$1,193.40