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	$91.77	8.854%	$99.8953	$99.90	$99.90	$99.90
Purchase #2	$111.83	13.806%	$127.2692	$127.27	$127.25	$127.30
Purchase #3	$33.70	12.232%	$37.8222	$37.82	$37.80	$37.80
Purchase #4	$183.28	7.597%	$197.2038	$197.20	$197.20	$197.20
Purchase #5	$132.49	10.432%	$146.3114	$146.31	$146.30	$146.30
Purchase #6	$210.38	7.672%	$226.5204	$226.52	$226.50	$226.50
Purchase #7	$158.94	6.794%	$169.7384	$169.74	$169.75	$169.70
7 purchase totals =	$922.39		$1,004.7607	$1,004.76	$1,004.70	$1,004.70