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	$222.65	3.479%	$230.396	$230.40	$230.40	$230.40
Purchase #2	$56.81	5.364%	$59.8573	$59.86	$59.85	$59.90
Purchase #3	$136.85	4.830%	$143.4599	$143.46	$143.45	$143.50
Purchase #4	$208.34	3.426%	$215.4777	$215.48	$215.50	$215.50
Purchase #5	$71.84	6.874%	$76.7783	$76.78	$76.80	$76.80
Purchase #6	$66.61	9.120%	$72.6848	$72.68	$72.70	$72.70
Purchase #7	$117.49	5.673%	$124.1552	$124.16	$124.15	$124.20
7 purchase totals =	$880.59		$922.8092	$922.82	$922.85	$923.00