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	$154.92	7.501%	$166.5405	$166.54	$166.55	$166.50
Purchase #2	$191.30	13.300%	$216.7429	$216.74	$216.75	$216.70
Purchase #3	$140.31	9.776%	$154.0267	$154.03	$154.05	$154.00
Purchase #4	$179.34	7.295%	$192.4229	$192.42	$192.40	$192.40
Purchase #5	$248.89	10.633%	$275.3545	$275.35	$275.35	$275.40
Purchase #6	$66.48	8.719%	$72.2764	$72.28	$72.30	$72.30
Purchase #7	$61.53	8.512%	$66.7674	$66.77	$66.75	$66.80
7 purchase totals =	$1,042.77		$1,144.1313	$1,144.13	$1,144.15	$1,144.10