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	$224.44	8.393%	$243.2772	$243.28	$243.30	$243.30
Purchase #2	$44.63	6.317%	$47.4493	$47.45	$47.45	$47.40
Purchase #3	$240.33	3.399%	$248.4988	$248.50	$248.50	$248.50
Purchase #4	$225.70	11.592%	$251.8631	$251.86	$251.85	$251.90
Purchase #5	$177.34	6.761%	$189.33	$189.33	$189.35	$189.30
Purchase #6	$42.76	7.243%	$45.8571	$45.86	$45.85	$45.90
Purchase #7	$18.81	6.849%	$20.0983	$20.10	$20.10	$20.10
7 purchase totals =	$974.01		$1,046.3738	$1,046.38	$1,046.40	$1,046.40