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	$166.52	11.458%	$185.5999	$185.60	$185.60	$185.60
Purchase #2	$25.29	5.118%	$26.5843	$26.58	$26.60	$26.60
Purchase #3	$150.34	3.644%	$155.8184	$155.82	$155.80	$155.80
Purchase #4	$150.32	10.218%	$165.6797	$165.68	$165.70	$165.70
Purchase #5	$156.25	12.162%	$175.2531	$175.25	$175.25	$175.30
Purchase #6	$56.92	8.380%	$61.6899	$61.69	$61.70	$61.70
Purchase #7	$29.31	8.857%	$31.906	$31.91	$31.90	$31.90
7 purchase totals =	$734.95		$802.5313	$802.53	$802.55	$802.60