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	$124.83	12.231%	$140.098	$140.10	$140.10	$140.10
Purchase #2	$225.94	8.242%	$244.562	$244.56	$244.55	$244.60
Purchase #3	$180.39	4.434%	$188.3885	$188.39	$188.40	$188.40
Purchase #4	$145.61	9.818%	$159.906	$159.91	$159.90	$159.90
Purchase #5	$80.41	6.534%	$85.664	$85.66	$85.65	$85.70
Purchase #6	$134.55	13.346%	$152.507	$152.51	$152.50	$152.50
Purchase #7	$11.66	5.598%	$12.3127	$12.31	$12.30	$12.30
7 purchase totals =	$903.39		$983.4382	$983.44	$983.40	$983.50