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	$147.82	6.681%	$157.6959	$157.70	$157.70	$157.70
Purchase #2	$53.34	10.558%	$58.9716	$58.97	$58.95	$59.00
Purchase #3	$226.77	7.503%	$243.7846	$243.78	$243.80	$243.80
Purchase #4	$189.43	3.685%	$196.4105	$196.41	$196.40	$196.40
Purchase #5	$146.37	12.402%	$164.5228	$164.52	$164.50	$164.50
Purchase #6	$64.70	4.218%	$67.429	$67.43	$67.45	$67.40
Purchase #7	$213.48	12.205%	$239.5352	$239.54	$239.55	$239.50
7 purchase totals =	$1,041.91		$1,128.3496	$1,128.35	$1,128.35	$1,128.30