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	$130.64	3.233%	$134.8636	$134.86	$134.85	$134.90
Purchase #2	$29.83	10.763%	$33.0406	$33.04	$33.05	$33.00
Purchase #3	$157.56	6.147%	$167.2452	$167.25	$167.25	$167.20
Purchase #4	$40.59	3.801%	$42.1328	$42.13	$42.15	$42.10
Purchase #5	$64.74	9.843%	$71.1124	$71.11	$71.10	$71.10
Purchase #6	$126.73	6.336%	$134.7596	$134.76	$134.75	$134.80
Purchase #7	$140.56	13.552%	$159.6087	$159.61	$159.60	$159.60
7 purchase totals =	$690.65		$742.7629	$742.76	$742.75	$742.70