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	$181.66	13.712%	$206.5692	$206.57	$206.55	$206.60
Purchase #2	$225.94	12.235%	$253.5838	$253.58	$253.60	$253.60
Purchase #3	$47.85	6.799%	$51.1033	$51.10	$51.10	$51.10
Purchase #4	$27.53	4.311%	$28.7168	$28.72	$28.70	$28.70
Purchase #5	$30.48	11.163%	$33.8825	$33.88	$33.90	$33.90
Purchase #6	$86.83	5.616%	$91.7064	$91.71	$91.70	$91.70
Purchase #7	$62.96	13.563%	$71.4993	$71.50	$71.50	$71.50
7 purchase totals =	$663.25		$737.0613	$737.06	$737.05	$737.10