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	$140.89	3.676%	$146.0691	$146.07	$146.05	$146.10
Purchase #2	$195.76	4.376%	$204.3265	$204.33	$204.35	$204.30
Purchase #3	$195.43	8.153%	$211.3634	$211.36	$211.35	$211.40
Purchase #4	$31.59	5.508%	$33.33	$33.33	$33.35	$33.30
Purchase #5	$95.32	4.568%	$99.6742	$99.67	$99.65	$99.70
Purchase #6	$57.96	3.431%	$59.9486	$59.95	$59.95	$59.90
Purchase #7	$34.37	9.220%	$37.5389	$37.54	$37.55	$37.50
7 purchase totals =	$751.32		$792.2507	$792.25	$792.25	$792.20