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	$123.40	3.619%	$127.8658	$127.87	$127.85	$127.90
Purchase #2	$31.72	8.611%	$34.4514	$34.45	$34.45	$34.50
Purchase #3	$212.78	8.681%	$231.2514	$231.25	$231.25	$231.30
Purchase #4	$86.92	10.574%	$96.1109	$96.11	$96.10	$96.10
Purchase #5	$172.54	13.158%	$195.2428	$195.24	$195.25	$195.20
Purchase #6	$212.39	5.108%	$223.2389	$223.24	$223.25	$223.20
Purchase #7	$124.89	4.321%	$130.2865	$130.29	$130.30	$130.30
7 purchase totals =	$964.64		$1,038.4477	$1,038.45	$1,038.45	$1,038.50