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	$98.42	8.642%	$106.9255	$106.93	$106.95	$106.90
Purchase #2	$42.58	6.461%	$45.3311	$45.33	$45.35	$45.30
Purchase #3	$58.72	9.731%	$64.434	$64.43	$64.45	$64.40
Purchase #4	$52.41	3.622%	$54.3083	$54.31	$54.30	$54.30
Purchase #5	$42.83	7.382%	$45.9917	$45.99	$46.00	$46.00
Purchase #6	$69.88	11.488%	$77.9078	$77.91	$77.90	$77.90
Purchase #7	$92.88	4.776%	$97.3159	$97.32	$97.30	$97.30
7 purchase totals =	$457.72		$492.2143	$492.22	$492.25	$492.10