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	$84.97	10.147%	$93.5919	$93.59	$93.60	$93.60
Purchase #2	$125.69	4.707%	$131.6062	$131.61	$131.60	$131.60
Purchase #3	$106.34	3.711%	$110.2863	$110.29	$110.30	$110.30
Purchase #4	$99.36	5.772%	$105.0951	$105.10	$105.10	$105.10
Purchase #5	$124.98	13.309%	$141.6136	$141.61	$141.60	$141.60
Purchase #6	$218.56	3.864%	$227.0052	$227.01	$227.00	$227.00
Purchase #7	$134.28	5.204%	$141.2679	$141.27	$141.25	$141.30
7 purchase totals =	$894.18		$950.4662	$950.48	$950.45	$950.50