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	$24.45	4.865%	$25.6395	$25.64	$25.65	$25.60
Purchase #2	$56.41	9.438%	$61.734	$61.73	$61.75	$61.70
Purchase #3	$236.72	11.792%	$264.634	$264.63	$264.65	$264.60
Purchase #4	$103.86	5.280%	$109.3438	$109.34	$109.35	$109.30
Purchase #5	$56.97	6.353%	$60.5893	$60.59	$60.60	$60.60
Purchase #6	$206.50	10.536%	$228.2568	$228.26	$228.25	$228.30
Purchase #7	$77.28	10.641%	$85.5034	$85.50	$85.50	$85.50
7 purchase totals =	$762.19		$835.7008	$835.69	$835.75	$835.60