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	$30.26	11.634%	$33.7804	$33.78	$33.80	$33.80
Purchase #2	$153.94	3.512%	$159.3464	$159.35	$159.35	$159.30
Purchase #3	$62.29	3.570%	$64.5138	$64.51	$64.50	$64.50
Purchase #4	$241.57	13.820%	$274.955	$274.96	$274.95	$275.00
Purchase #5	$183.32	3.855%	$190.387	$190.39	$190.40	$190.40
Purchase #6	$123.35	13.352%	$139.8197	$139.82	$139.80	$139.80
Purchase #7	$50.88	10.321%	$56.1313	$56.13	$56.15	$56.10
7 purchase totals =	$845.61		$918.9336	$918.94	$918.95	$918.90