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	$99.76	7.113%	$106.8559	$106.86	$106.85	$106.90
Purchase #2	$52.54	13.263%	$59.5084	$59.51	$59.50	$59.50
Purchase #3	$205.75	7.341%	$220.8541	$220.85	$220.85	$220.90
Purchase #4	$200.66	13.837%	$228.4253	$228.43	$228.45	$228.40
Purchase #5	$135.61	7.500%	$145.7808	$145.78	$145.80	$145.80
Purchase #6	$221.74	9.793%	$243.455	$243.46	$243.45	$243.50
Purchase #7	$187.43	4.306%	$195.5007	$195.50	$195.50	$195.50
7 purchase totals =	$1,103.49		$1,200.3802	$1,200.39	$1,200.40	$1,200.50