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	$219.79	13.132%	$248.6528	$248.65	$248.65	$248.70
Purchase #2	$222.78	10.700%	$246.6175	$246.62	$246.60	$246.60
Purchase #3	$61.79	13.350%	$70.039	$70.04	$70.05	$70.00
Purchase #4	$78.39	4.712%	$82.0837	$82.08	$82.10	$82.10
Purchase #5	$83.50	6.536%	$88.9576	$88.96	$88.95	$89.00
Purchase #6	$214.64	4.164%	$223.5776	$223.58	$223.60	$223.60
Purchase #7	$201.81	10.765%	$223.5348	$223.53	$223.55	$223.50
7 purchase totals =	$1,082.70		$1,183.4630	$1,183.46	$1,183.50	$1,183.50