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	$145.94	4.222%	$152.1016	$152.10	$152.10	$152.10
Purchase #2	$238.56	3.777%	$247.5704	$247.57	$247.55	$247.60
Purchase #3	$183.89	9.397%	$201.1701	$201.17	$201.15	$201.20
Purchase #4	$23.41	5.805%	$24.769	$24.77	$24.75	$24.80
Purchase #5	$94.38	7.528%	$101.4849	$101.48	$101.50	$101.50
Purchase #6	$200.59	13.330%	$227.3286	$227.33	$227.35	$227.30
Purchase #7	$117.39	11.489%	$130.8769	$130.88	$130.90	$130.90
7 purchase totals =	$1,004.16		$1,085.3015	$1,085.30	$1,085.30	$1,085.40