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	$85.50	8.175%	$92.4896	$92.49	$92.50	$92.50
Purchase #2	$196.46	13.372%	$222.7306	$222.73	$222.75	$222.70
Purchase #3	$215.71	11.846%	$241.263	$241.26	$241.25	$241.30
Purchase #4	$26.86	7.386%	$28.8439	$28.84	$28.85	$28.80
Purchase #5	$49.81	11.206%	$55.3917	$55.39	$55.40	$55.40
Purchase #6	$134.51	7.341%	$144.3844	$144.38	$144.40	$144.40
Purchase #7	$221.69	4.762%	$232.2469	$232.25	$232.25	$232.20
7 purchase totals =	$930.54		$1,017.3501	$1,017.34	$1,017.40	$1,017.30