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	$247.85	6.403%	$263.7198	$263.72	$263.70	$263.70
Purchase #2	$182.88	7.291%	$196.2138	$196.21	$196.20	$196.20
Purchase #3	$225.51	10.377%	$248.9112	$248.91	$248.90	$248.90
Purchase #4	$135.46	5.303%	$142.6434	$142.64	$142.65	$142.60
Purchase #5	$138.44	7.366%	$148.6375	$148.64	$148.65	$148.60
Purchase #6	$117.83	4.786%	$123.4693	$123.47	$123.45	$123.50
Purchase #7	$224.33	9.173%	$244.9078	$244.91	$244.90	$244.90
7 purchase totals =	$1,272.30		$1,368.5028	$1,368.50	$1,368.45	$1,368.40