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	$217.71	13.226%	$246.5043	$246.50	$246.50	$246.50
Purchase #2	$105.79	3.539%	$109.5339	$109.53	$109.55	$109.50
Purchase #3	$185.71	5.656%	$196.2138	$196.21	$196.20	$196.20
Purchase #4	$86.44	9.157%	$94.3553	$94.36	$94.35	$94.40
Purchase #5	$54.90	11.226%	$61.0631	$61.06	$61.05	$61.10
Purchase #6	$17.44	6.235%	$18.5274	$18.53	$18.55	$18.50
Purchase #7	$40.56	13.475%	$46.0255	$46.03	$46.05	$46.00
7 purchase totals =	$708.55		$772.2233	$772.22	$772.25	$772.20