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	$87.90	9.532%	$96.2786	$96.28	$96.30	$96.30
Purchase #2	$39.38	10.191%	$43.3932	$43.39	$43.40	$43.40
Purchase #3	$81.81	9.224%	$89.3562	$89.36	$89.35	$89.40
Purchase #4	$96.64	11.865%	$108.1063	$108.11	$108.10	$108.10
Purchase #5	$121.36	7.490%	$130.4499	$130.45	$130.45	$130.40
Purchase #6	$209.44	10.559%	$231.5548	$231.55	$231.55	$231.60
Purchase #7	$130.83	10.367%	$144.3931	$144.39	$144.40	$144.40
7 purchase totals =	$767.36		$843.5321	$843.53	$843.55	$843.60