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	$190.27	10.612%	$210.4615	$210.46	$210.45	$210.50
Purchase #2	$10.58	10.113%	$11.65	$11.65	$11.65	$11.70
Purchase #3	$220.27	10.562%	$243.5349	$243.53	$243.55	$243.50
Purchase #4	$250.60	13.873%	$285.3657	$285.37	$285.35	$285.40
Purchase #5	$168.81	7.663%	$181.7459	$181.75	$181.75	$181.70
Purchase #6	$142.80	8.746%	$155.2893	$155.29	$155.30	$155.30
Purchase #7	$248.54	4.790%	$260.4451	$260.45	$260.45	$260.40
7 purchase totals =	$1,231.87		$1,348.4924	$1,348.50	$1,348.50	$1,348.50