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	$176.35	3.516%	$182.5505	$182.55	$182.55	$182.60
Purchase #2	$27.25	8.697%	$29.6199	$29.62	$29.60	$29.60
Purchase #3	$102.52	4.304%	$106.9325	$106.93	$106.95	$106.90
Purchase #4	$237.51	6.670%	$253.3519	$253.35	$253.35	$253.40
Purchase #5	$90.52	8.621%	$98.3237	$98.32	$98.30	$98.30
Purchase #6	$216.72	9.852%	$238.0713	$238.07	$238.05	$238.10
Purchase #7	$236.42	8.236%	$255.8916	$255.89	$255.90	$255.90
7 purchase totals =	$1,087.29		$1,164.7414	$1,164.73	$1,164.70	$1,164.80