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	$26.45	4.865%	$27.7368	$27.74	$27.75	$27.70
Purchase #2	$88.70	7.573%	$95.4173	$95.42	$95.40	$95.40
Purchase #3	$137.65	6.496%	$146.5917	$146.59	$146.60	$146.60
Purchase #4	$55.99	6.345%	$59.5426	$59.54	$59.55	$59.50
Purchase #5	$136.73	11.799%	$152.8628	$152.86	$152.85	$152.90
Purchase #6	$84.49	8.630%	$91.7815	$91.78	$91.80	$91.80
Purchase #7	$115.68	4.856%	$121.2974	$121.30	$121.30	$121.30
7 purchase totals =	$645.69		$695.2301	$695.23	$695.25	$695.20