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	$139.32	13.727%	$158.4445	$158.44	$158.45	$158.40
Purchase #2	$172.29	7.766%	$185.67	$185.67	$185.65	$185.70
Purchase #3	$159.61	4.715%	$167.1356	$167.14	$167.15	$167.10
Purchase #4	$200.73	6.591%	$213.9601	$213.96	$213.95	$214.00
Purchase #5	$247.46	10.283%	$272.9063	$272.91	$272.90	$272.90
Purchase #6	$77.89	9.232%	$85.0808	$85.08	$85.10	$85.10
Purchase #7	$12.91	10.441%	$14.2579	$14.26	$14.25	$14.30
7 purchase totals =	$1,010.21		$1,097.4552	$1,097.46	$1,097.45	$1,097.50