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	$60.43	10.469%	$66.7564	$66.76	$66.75	$66.80
Purchase #2	$77.47	6.837%	$82.7666	$82.77	$82.75	$82.80
Purchase #3	$81.88	10.558%	$90.5249	$90.52	$90.50	$90.50
Purchase #4	$71.40	6.699%	$76.1831	$76.18	$76.20	$76.20
Purchase #5	$168.86	13.630%	$191.8756	$191.88	$191.90	$191.90
Purchase #6	$232.89	6.216%	$247.3664	$247.37	$247.35	$247.40
Purchase #7	$60.84	6.410%	$64.7398	$64.74	$64.75	$64.70
7 purchase totals =	$753.77		$820.2128	$820.22	$820.20	$820.30