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	$115.31	9.665%	$126.4547	$126.45	$126.45	$126.50
Purchase #2	$61.28	6.242%	$65.1051	$65.11	$65.10	$65.10
Purchase #3	$203.25	4.197%	$211.7804	$211.78	$211.80	$211.80
Purchase #4	$65.47	8.420%	$70.9826	$70.98	$71.00	$71.00
Purchase #5	$144.40	9.848%	$158.6205	$158.62	$158.60	$158.60
Purchase #6	$96.38	10.402%	$106.4054	$106.41	$106.40	$106.40
Purchase #7	$132.50	7.577%	$142.5395	$142.54	$142.55	$142.50
7 purchase totals =	$818.59		$881.8882	$881.89	$881.90	$881.90