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	$121.35	7.130%	$130.0023	$130.00	$130.00	$130.00
Purchase #2	$27.76	13.404%	$31.481	$31.48	$31.50	$31.50
Purchase #3	$147.96	13.732%	$168.2779	$168.28	$168.30	$168.30
Purchase #4	$194.32	12.493%	$218.5964	$218.60	$218.60	$218.60
Purchase #5	$118.65	8.327%	$128.53	$128.53	$128.55	$128.50
Purchase #6	$198.55	11.775%	$221.9293	$221.93	$221.95	$221.90
Purchase #7	$222.87	11.857%	$249.2957	$249.30	$249.30	$249.30
7 purchase totals =	$1,031.46		$1,148.1126	$1,148.12	$1,148.20	$1,148.10