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	$83.77	10.107%	$92.2366	$92.24	$92.25	$92.20
Purchase #2	$147.47	7.434%	$158.4329	$158.43	$158.45	$158.40
Purchase #3	$21.95	12.420%	$24.6762	$24.68	$24.70	$24.70
Purchase #4	$28.37	11.179%	$31.5415	$31.54	$31.55	$31.50
Purchase #5	$247.62	11.646%	$276.4578	$276.46	$276.45	$276.50
Purchase #6	$114.51	7.689%	$123.3147	$123.31	$123.30	$123.30
Purchase #7	$152.59	8.759%	$165.9554	$165.96	$165.95	$166.00
7 purchase totals =	$796.28		$872.6151	$872.62	$872.65	$872.60