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	$181.38	13.874%	$206.5447	$206.54	$206.55	$206.50
Purchase #2	$101.91	8.215%	$110.2819	$110.28	$110.30	$110.30
Purchase #3	$36.34	8.160%	$39.3053	$39.31	$39.30	$39.30
Purchase #4	$37.78	11.162%	$41.997	$42.00	$42.00	$42.00
Purchase #5	$50.90	12.562%	$57.2941	$57.29	$57.30	$57.30
Purchase #6	$35.98	4.312%	$37.5315	$37.53	$37.55	$37.50
Purchase #7	$217.58	11.360%	$242.2971	$242.30	$242.30	$242.30
7 purchase totals =	$661.87		$735.2516	$735.25	$735.30	$735.20