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	$162.93	5.356%	$171.6565	$171.66	$171.65	$171.70
Purchase #2	$207.85	11.809%	$232.395	$232.40	$232.40	$232.40
Purchase #3	$73.46	9.824%	$80.6767	$80.68	$80.70	$80.70
Purchase #4	$81.77	9.263%	$89.3444	$89.34	$89.35	$89.30
Purchase #5	$12.82	6.200%	$13.6148	$13.61	$13.60	$13.60
Purchase #6	$175.82	5.683%	$185.8119	$185.81	$185.80	$185.80
Purchase #7	$92.72	7.814%	$99.9651	$99.97	$99.95	$100.00
7 purchase totals =	$807.37		$873.4644	$873.47	$873.45	$873.50