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	$55.94	11.610%	$62.4346	$62.43	$62.45	$62.40
Purchase #2	$91.86	9.168%	$100.2817	$100.28	$100.30	$100.30
Purchase #3	$76.90	8.726%	$83.6103	$83.61	$83.60	$83.60
Purchase #4	$6.73	10.776%	$7.4552	$7.46	$7.45	$7.50
Purchase #5	$120.89	5.344%	$127.3504	$127.35	$127.35	$127.40
Purchase #6	$169.40	8.351%	$183.5466	$183.55	$183.55	$183.50
Purchase #7	$101.26	4.441%	$105.757	$105.76	$105.75	$105.80
7 purchase totals =	$622.98		$670.4358	$670.44	$670.45	$670.50