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	$81.45	4.465%	$85.0867	$85.09	$85.10	$85.10
Purchase #2	$84.50	7.130%	$90.5249	$90.52	$90.50	$90.50
Purchase #3	$84.54	10.240%	$93.1969	$93.20	$93.20	$93.20
Purchase #4	$61.61	10.674%	$68.1863	$68.19	$68.20	$68.20
Purchase #5	$65.55	10.570%	$72.4786	$72.48	$72.50	$72.50
Purchase #6	$145.52	5.266%	$153.1831	$153.18	$153.20	$153.20
Purchase #7	$149.78	3.736%	$155.3758	$155.38	$155.40	$155.40
7 purchase totals =	$672.95		$718.0323	$718.04	$718.10	$718.10