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	$66.52	9.403%	$72.7749	$72.77	$72.75	$72.80
Purchase #2	$96.35	13.872%	$109.7157	$109.72	$109.70	$109.70
Purchase #3	$51.72	3.523%	$53.5421	$53.54	$53.55	$53.50
Purchase #4	$26.42	13.349%	$29.9468	$29.95	$29.95	$29.90
Purchase #5	$153.41	11.714%	$171.3804	$171.38	$171.40	$171.40
Purchase #6	$245.56	7.832%	$264.7923	$264.79	$264.80	$264.80
Purchase #7	$87.85	8.215%	$95.0669	$95.07	$95.05	$95.10
7 purchase totals =	$727.83		$797.2191	$797.22	$797.20	$797.20