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	$199.48	7.146%	$213.7348	$213.73	$213.75	$213.70
Purchase #2	$228.41	4.361%	$238.371	$238.37	$238.35	$238.40
Purchase #3	$63.83	10.607%	$70.6004	$70.60	$70.60	$70.60
Purchase #4	$213.90	4.408%	$223.3287	$223.33	$223.35	$223.30
Purchase #5	$38.28	4.117%	$39.856	$39.86	$39.85	$39.90
Purchase #6	$51.62	7.224%	$55.349	$55.35	$55.35	$55.30
Purchase #7	$141.97	5.830%	$150.2469	$150.25	$150.25	$150.20
7 purchase totals =	$937.49		$991.4868	$991.49	$991.50	$991.40