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	$61.78	6.760%	$65.9563	$65.96	$65.95	$66.00
Purchase #2	$107.31	10.512%	$118.5904	$118.59	$118.60	$118.60
Purchase #3	$34.31	8.650%	$37.2778	$37.28	$37.30	$37.30
Purchase #4	$209.71	5.178%	$220.5688	$220.57	$220.55	$220.60
Purchase #5	$232.72	11.277%	$258.9638	$258.96	$258.95	$259.00
Purchase #6	$45.84	4.454%	$47.8817	$47.88	$47.90	$47.90
Purchase #7	$143.63	6.368%	$152.7764	$152.78	$152.80	$152.80
7 purchase totals =	$835.30		$902.0152	$902.02	$902.05	$902.20