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	$195.50	13.148%	$221.2043	$221.20	$221.20	$221.20
Purchase #2	$81.33	5.760%	$86.0146	$86.01	$86.00	$86.00
Purchase #3	$202.90	9.641%	$222.4616	$222.46	$222.45	$222.50
Purchase #4	$29.95	12.190%	$33.6009	$33.60	$33.60	$33.60
Purchase #5	$148.29	5.785%	$156.8686	$156.87	$156.85	$156.90
Purchase #6	$87.41	13.765%	$99.442	$99.44	$99.45	$99.40
Purchase #7	$148.97	3.795%	$154.6234	$154.62	$154.60	$154.60
7 purchase totals =	$894.35		$974.2154	$974.20	$974.15	$974.20