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	$162.35	3.123%	$167.4202	$167.42	$167.40	$167.40
Purchase #2	$248.84	7.429%	$267.3263	$267.33	$267.35	$267.30
Purchase #3	$243.71	5.137%	$256.2294	$256.23	$256.25	$256.20
Purchase #4	$120.88	9.110%	$131.8922	$131.89	$131.90	$131.90
Purchase #5	$40.90	9.253%	$44.6845	$44.68	$44.70	$44.70
Purchase #6	$124.56	12.200%	$139.7563	$139.76	$139.75	$139.80
Purchase #7	$92.82	13.786%	$105.6162	$105.62	$105.60	$105.60
7 purchase totals =	$1,034.06		$1,112.9251	$1,112.93	$1,112.95	$1,112.90