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	$136.33	3.196%	$140.6871	$140.69	$140.70	$140.70
Purchase #2	$31.32	12.183%	$35.1357	$35.14	$35.15	$35.10
Purchase #3	$189.65	12.104%	$212.6052	$212.61	$212.60	$212.60
Purchase #4	$80.88	13.707%	$91.9662	$91.97	$91.95	$92.00
Purchase #5	$56.56	8.402%	$61.3122	$61.31	$61.30	$61.30
Purchase #6	$155.81	9.183%	$170.118	$170.12	$170.10	$170.10
Purchase #7	$48.73	11.188%	$54.1819	$54.18	$54.20	$54.20
7 purchase totals =	$699.28		$766.0063	$766.02	$766.00	$766.00