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	$197.73	13.856%	$225.1275	$225.13	$225.15	$225.10
Purchase #2	$233.40	12.569%	$262.736	$262.74	$262.75	$262.70
Purchase #3	$74.38	10.548%	$82.2256	$82.23	$82.25	$82.20
Purchase #4	$243.94	7.526%	$262.2989	$262.30	$262.30	$262.30
Purchase #5	$21.55	7.404%	$23.1456	$23.15	$23.15	$23.10
Purchase #6	$41.70	4.687%	$43.6545	$43.65	$43.65	$43.70
Purchase #7	$42.56	6.489%	$45.3217	$45.32	$45.30	$45.30
7 purchase totals =	$855.26		$944.5098	$944.52	$944.55	$944.40