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	$215.63	5.394%	$227.2611	$227.26	$227.25	$227.30
Purchase #2	$136.97	10.856%	$151.8395	$151.84	$151.85	$151.80
Purchase #3	$194.83	9.258%	$212.8674	$212.87	$212.85	$212.90
Purchase #4	$176.56	7.705%	$190.1639	$190.16	$190.15	$190.20
Purchase #5	$220.48	4.144%	$229.6167	$229.62	$229.60	$229.60
Purchase #6	$144.57	5.729%	$152.8524	$152.85	$152.85	$152.90
Purchase #7	$144.94	5.180%	$152.4479	$152.45	$152.45	$152.40
7 purchase totals =	$1,233.98		$1,317.0489	$1,317.05	$1,317.00	$1,317.10