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	$214.33	6.717%	$228.7265	$228.73	$228.75	$228.70
Purchase #2	$211.52	5.795%	$223.7776	$223.78	$223.80	$223.80
Purchase #3	$92.40	8.116%	$99.8992	$99.90	$99.90	$99.90
Purchase #4	$112.79	12.776%	$127.2001	$127.20	$127.20	$127.20
Purchase #5	$190.94	12.658%	$215.1092	$215.11	$215.10	$215.10
Purchase #6	$175.87	11.526%	$196.1408	$196.14	$196.15	$196.10
Purchase #7	$166.31	11.281%	$185.0714	$185.07	$185.05	$185.10
7 purchase totals =	$1,164.16		$1,275.9248	$1,275.93	$1,275.95	$1,275.90