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	$38.38	8.563%	$41.6665	$41.67	$41.65	$41.70
Purchase #2	$216.79	12.729%	$244.3852	$244.39	$244.40	$244.40
Purchase #3	$171.45	6.709%	$182.9526	$182.95	$182.95	$183.00
Purchase #4	$165.73	11.325%	$184.4989	$184.50	$184.50	$184.50
Purchase #5	$225.65	12.288%	$253.3779	$253.38	$253.40	$253.40
Purchase #6	$39.59	7.118%	$42.408	$42.41	$42.40	$42.40
Purchase #7	$98.30	11.500%	$109.6045	$109.60	$109.60	$109.60
7 purchase totals =	$955.89		$1,058.8936	$1,058.90	$1,058.90	$1,059.00