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	$98.28	10.500%	$108.5994	$108.60	$108.60	$108.60
Purchase #2	$83.61	10.632%	$92.4994	$92.50	$92.50	$92.50
Purchase #3	$26.87	10.813%	$29.7755	$29.78	$29.80	$29.80
Purchase #4	$77.46	5.700%	$81.8752	$81.88	$81.90	$81.90
Purchase #5	$159.80	5.561%	$168.6865	$168.69	$168.70	$168.70
Purchase #6	$60.47	11.457%	$67.398	$67.40	$67.40	$67.40
Purchase #7	$75.81	9.733%	$83.1886	$83.19	$83.20	$83.20
7 purchase totals =	$582.30		$632.0226	$632.04	$632.10	$632.10