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	$58.25	7.329%	$62.5191	$62.52	$62.50	$62.50
Purchase #2	$37.50	12.871%	$42.3266	$42.33	$42.35	$42.30
Purchase #3	$237.57	5.326%	$250.223	$250.22	$250.20	$250.20
Purchase #4	$160.94	13.426%	$182.5478	$182.55	$182.55	$182.50
Purchase #5	$157.91	13.145%	$178.6673	$178.67	$178.65	$178.70
Purchase #6	$250.83	11.598%	$279.9213	$279.92	$279.90	$279.90
Purchase #7	$222.87	11.642%	$248.8165	$248.82	$248.80	$248.80
7 purchase totals =	$1,125.87		$1,245.0216	$1,245.03	$1,244.95	$1,244.90