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	$57.73	10.785%	$63.9562	$63.96	$63.95	$64.00
Purchase #2	$178.41	12.491%	$200.6952	$200.70	$200.70	$200.70
Purchase #3	$40.32	10.512%	$44.5584	$44.56	$44.55	$44.60
Purchase #4	$81.67	10.450%	$90.2045	$90.20	$90.20	$90.20
Purchase #5	$162.31	3.773%	$168.434	$168.43	$168.45	$168.40
Purchase #6	$238.87	10.609%	$264.2117	$264.21	$264.20	$264.20
Purchase #7	$151.90	11.589%	$169.5037	$169.50	$169.50	$169.50
7 purchase totals =	$911.21		$1,001.5637	$1,001.56	$1,001.55	$1,001.60