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	$200.63	4.198%	$209.0524	$209.05	$209.05	$209.10
Purchase #2	$159.28	6.191%	$169.141	$169.14	$169.15	$169.10
Purchase #3	$217.48	4.687%	$227.6733	$227.67	$227.65	$227.70
Purchase #4	$53.47	10.372%	$59.0159	$59.02	$59.00	$59.00
Purchase #5	$132.36	10.289%	$145.9785	$145.98	$146.00	$146.00
Purchase #6	$149.31	11.604%	$166.6359	$166.64	$166.65	$166.60
Purchase #7	$151.95	10.725%	$168.2466	$168.25	$168.25	$168.20
7 purchase totals =	$1,064.48		$1,145.7436	$1,145.75	$1,145.75	$1,145.70