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	$152.27	11.155%	$169.2557	$169.26	$169.25	$169.30
Purchase #2	$223.38	10.226%	$246.2228	$246.22	$246.20	$246.20
Purchase #3	$16.69	13.300%	$18.9098	$18.91	$18.90	$18.90
Purchase #4	$143.55	4.756%	$150.3772	$150.38	$150.40	$150.40
Purchase #5	$218.27	11.319%	$242.976	$242.98	$243.00	$243.00
Purchase #6	$73.79	6.644%	$78.6926	$78.69	$78.70	$78.70
Purchase #7	$111.32	9.619%	$122.0279	$122.03	$122.05	$122.00
7 purchase totals =	$939.27		$1,028.4620	$1,028.47	$1,028.50	$1,028.50