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	$32.83	13.265%	$37.1849	$37.18	$37.20	$37.20
Purchase #2	$126.73	6.698%	$135.2184	$135.22	$135.20	$135.20
Purchase #3	$128.80	6.774%	$137.5249	$137.52	$137.50	$137.50
Purchase #4	$39.51	10.867%	$43.8036	$43.80	$43.80	$43.80
Purchase #5	$144.56	12.666%	$162.87	$162.87	$162.85	$162.90
Purchase #6	$64.28	3.264%	$66.3781	$66.38	$66.40	$66.40
Purchase #7	$158.42	7.865%	$170.8797	$170.88	$170.90	$170.90
7 purchase totals =	$695.13		$753.8596	$753.85	$753.85	$753.90