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	$200.88	12.368%	$225.7248	$225.72	$225.70	$225.70
Purchase #2	$79.67	13.622%	$90.5226	$90.52	$90.50	$90.50
Purchase #3	$39.79	7.550%	$42.7941	$42.79	$42.80	$42.80
Purchase #4	$111.41	7.566%	$119.8393	$119.84	$119.85	$119.80
Purchase #5	$239.32	12.412%	$269.0244	$269.02	$269.00	$269.00
Purchase #6	$23.95	6.434%	$25.4909	$25.49	$25.50	$25.50
Purchase #7	$183.33	13.374%	$207.8486	$207.85	$207.85	$207.80
7 purchase totals =	$878.35		$981.2447	$981.23	$981.20	$981.10