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	$31.54	7.565%	$33.926	$33.93	$33.95	$33.90
Purchase #2	$104.55	8.353%	$113.2831	$113.28	$113.30	$113.30
Purchase #3	$58.38	12.861%	$65.8883	$65.89	$65.90	$65.90
Purchase #4	$233.29	13.196%	$264.0749	$264.07	$264.05	$264.10
Purchase #5	$49.56	4.209%	$51.646	$51.65	$51.65	$51.60
Purchase #6	$162.30	10.810%	$179.8446	$179.84	$179.85	$179.80
Purchase #7	$42.75	5.403%	$45.0598	$45.06	$45.05	$45.10
7 purchase totals =	$682.37		$753.7227	$753.72	$753.75	$753.70