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	$89.71	3.411%	$92.77	$92.77	$92.75	$92.80
Purchase #2	$49.27	12.320%	$55.3401	$55.34	$55.35	$55.30
Purchase #3	$40.51	4.620%	$42.3816	$42.38	$42.40	$42.40
Purchase #4	$50.40	6.290%	$53.5702	$53.57	$53.55	$53.60
Purchase #5	$42.55	5.353%	$44.8277	$44.83	$44.85	$44.80
Purchase #6	$13.89	13.342%	$15.7432	$15.74	$15.75	$15.70
Purchase #7	$182.80	6.155%	$194.0513	$194.05	$194.05	$194.10
7 purchase totals =	$469.13		$498.6841	$498.68	$498.70	$498.70