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	$54.48	13.449%	$61.807	$61.81	$61.80	$61.80
Purchase #2	$147.49	7.559%	$158.6388	$158.64	$158.65	$158.60
Purchase #3	$179.80	6.638%	$191.7351	$191.74	$191.75	$191.70
Purchase #4	$248.59	3.202%	$256.5499	$256.55	$256.55	$256.50
Purchase #5	$18.87	8.509%	$20.4756	$20.48	$20.50	$20.50
Purchase #6	$230.28	6.374%	$244.958	$244.96	$244.95	$245.00
Purchase #7	$136.41	4.137%	$142.0533	$142.05	$142.05	$142.10
7 purchase totals =	$1,015.92		$1,076.2177	$1,076.23	$1,076.25	$1,076.20