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	$229.45	5.674%	$242.469	$242.47	$242.45	$242.50
Purchase #2	$75.90	5.203%	$79.8491	$79.85	$79.85	$79.80
Purchase #3	$170.66	5.365%	$179.8159	$179.82	$179.80	$179.80
Purchase #4	$75.75	9.347%	$82.8304	$82.83	$82.85	$82.80
Purchase #5	$132.35	11.468%	$147.5279	$147.53	$147.55	$147.50
Purchase #6	$187.87	9.184%	$205.124	$205.12	$205.10	$205.10
Purchase #7	$130.89	13.665%	$148.7761	$148.78	$148.80	$148.80
7 purchase totals =	$1,002.87		$1,086.3924	$1,086.40	$1,086.40	$1,086.30