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	$146.64	9.158%	$160.0693	$160.07	$160.05	$160.10
Purchase #2	$242.50	8.545%	$263.2216	$263.22	$263.20	$263.20
Purchase #3	$88.31	8.605%	$95.9091	$95.91	$95.90	$95.90
Purchase #4	$130.80	12.620%	$147.307	$147.31	$147.30	$147.30
Purchase #5	$37.53	13.109%	$42.4498	$42.45	$42.45	$42.40
Purchase #6	$150.51	11.216%	$167.3912	$167.39	$167.40	$167.40
Purchase #7	$25.52	8.404%	$27.6647	$27.66	$27.65	$27.70
7 purchase totals =	$821.81		$904.0127	$904.01	$903.95	$904.00