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	$119.96	9.173%	$130.9639	$130.96	$130.95	$131.00
Purchase #2	$64.86	4.707%	$67.913	$67.91	$67.90	$67.90
Purchase #3	$162.40	10.840%	$180.0042	$180.00	$180.00	$180.00
Purchase #4	$153.51	10.582%	$169.7544	$169.75	$169.75	$169.80
Purchase #5	$150.98	3.402%	$156.1163	$156.12	$156.10	$156.10
Purchase #6	$244.64	3.538%	$253.2954	$253.30	$253.30	$253.30
Purchase #7	$87.69	13.503%	$99.5308	$99.53	$99.55	$99.50
7 purchase totals =	$984.04		$1,057.5780	$1,057.57	$1,057.55	$1,057.60