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	$155.99	7.261%	$167.3164	$167.32	$167.30	$167.30
Purchase #2	$242.31	11.872%	$271.077	$271.08	$271.10	$271.10
Purchase #3	$7.84	6.462%	$8.3466	$8.35	$8.35	$8.30
Purchase #4	$234.94	3.360%	$242.834	$242.83	$242.85	$242.80
Purchase #5	$133.91	12.199%	$150.2457	$150.25	$150.25	$150.20
Purchase #6	$157.91	4.712%	$165.3507	$165.35	$165.35	$165.40
Purchase #7	$34.69	7.601%	$37.3268	$37.33	$37.35	$37.30
7 purchase totals =	$967.59		$1,042.4972	$1,042.51	$1,042.55	$1,042.40