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	$206.41	10.713%	$228.5227	$228.52	$228.50	$228.50
Purchase #2	$136.83	11.285%	$152.2713	$152.27	$152.25	$152.30
Purchase #3	$158.43	5.741%	$167.5255	$167.53	$167.55	$167.50
Purchase #4	$222.26	8.189%	$240.4609	$240.46	$240.45	$240.50
Purchase #5	$174.81	5.348%	$184.1588	$184.16	$184.15	$184.20
Purchase #6	$140.56	11.270%	$156.4011	$156.40	$156.40	$156.40
Purchase #7	$88.34	5.226%	$92.9566	$92.96	$92.95	$93.00
7 purchase totals =	$1,127.64		$1,222.2969	$1,222.30	$1,222.25	$1,222.40