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	$117.65	11.860%	$131.6033	$131.60	$131.60	$131.60
Purchase #2	$71.47	9.363%	$78.1617	$78.16	$78.15	$78.20
Purchase #3	$204.45	7.841%	$220.4809	$220.48	$220.50	$220.50
Purchase #4	$223.45	6.275%	$237.4715	$237.47	$237.45	$237.50
Purchase #5	$54.30	3.711%	$56.3151	$56.32	$56.30	$56.30
Purchase #6	$68.59	10.359%	$75.6952	$75.70	$75.70	$75.70
Purchase #7	$89.36	10.593%	$98.8259	$98.83	$98.85	$98.80
7 purchase totals =	$829.27		$898.5536	$898.56	$898.55	$898.60