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	$185.25	10.512%	$204.7235	$204.72	$204.70	$204.70
Purchase #2	$47.97	8.394%	$51.9966	$52.00	$52.00	$52.00
Purchase #3	$207.42	11.134%	$230.5141	$230.51	$230.50	$230.50
Purchase #4	$40.40	6.263%	$42.9303	$42.93	$42.95	$42.90
Purchase #5	$10.58	6.764%	$11.2956	$11.30	$11.30	$11.30
Purchase #6	$168.37	13.310%	$190.78	$190.78	$190.80	$190.80
Purchase #7	$64.25	4.394%	$67.0731	$67.07	$67.05	$67.10
7 purchase totals =	$724.24		$799.3132	$799.31	$799.30	$799.30