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	$176.39	3.150%	$181.9463	$181.95	$181.95	$181.90
Purchase #2	$140.74	7.658%	$151.5179	$151.52	$151.50	$151.50
Purchase #3	$90.46	4.244%	$94.2991	$94.30	$94.30	$94.30
Purchase #4	$231.62	12.129%	$259.7132	$259.71	$259.70	$259.70
Purchase #5	$210.76	11.642%	$235.2967	$235.30	$235.30	$235.30
Purchase #6	$35.39	12.685%	$39.8792	$39.88	$39.90	$39.90
Purchase #7	$104.61	4.150%	$108.9513	$108.95	$108.95	$109.00
7 purchase totals =	$989.97		$1,071.6037	$1,071.61	$1,071.60	$1,071.60