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	$183.56	9.231%	$200.5044	$200.50	$200.50	$200.50
Purchase #2	$185.80	6.811%	$198.4548	$198.45	$198.45	$198.50
Purchase #3	$141.27	6.523%	$150.485	$150.49	$150.50	$150.50
Purchase #4	$247.89	7.414%	$266.2686	$266.27	$266.25	$266.30
Purchase #5	$192.96	12.336%	$216.7635	$216.76	$216.75	$216.80
Purchase #6	$79.46	10.133%	$87.5117	$87.51	$87.50	$87.50
Purchase #7	$185.79	4.807%	$194.7209	$194.72	$194.70	$194.70
7 purchase totals =	$1,216.73		$1,314.7089	$1,314.70	$1,314.65	$1,314.80