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	$119.29	6.374%	$126.8935	$126.89	$126.90	$126.90
Purchase #2	$225.96	13.425%	$256.2951	$256.30	$256.30	$256.30
Purchase #3	$98.64	11.739%	$110.2193	$110.22	$110.20	$110.20
Purchase #4	$35.54	13.369%	$40.2913	$40.29	$40.30	$40.30
Purchase #5	$110.66	11.169%	$123.0196	$123.02	$123.00	$123.00
Purchase #6	$139.69	4.713%	$146.2736	$146.27	$146.25	$146.30
Purchase #7	$231.99	6.645%	$247.4057	$247.41	$247.40	$247.40
7 purchase totals =	$961.77		$1,050.3981	$1,050.40	$1,050.35	$1,050.40