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	$139.78	3.759%	$145.0343	$145.03	$145.05	$145.00
Purchase #2	$143.40	5.413%	$151.1622	$151.16	$151.15	$151.20
Purchase #3	$32.89	13.544%	$37.3446	$37.34	$37.35	$37.30
Purchase #4	$53.63	7.296%	$57.5428	$57.54	$57.55	$57.50
Purchase #5	$85.32	13.777%	$97.0745	$97.07	$97.05	$97.10
Purchase #6	$183.76	8.440%	$199.2693	$199.27	$199.25	$199.30
Purchase #7	$222.28	6.544%	$236.826	$236.83	$236.85	$236.80
7 purchase totals =	$861.06		$924.2537	$924.24	$924.25	$924.20