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	$78.88	4.477%	$82.4115	$82.41	$82.40	$82.40
Purchase #2	$236.71	13.505%	$268.6777	$268.68	$268.70	$268.70
Purchase #3	$135.43	3.401%	$140.036	$140.04	$140.05	$140.00
Purchase #4	$162.39	10.559%	$179.5368	$179.54	$179.55	$179.50
Purchase #5	$36.32	12.807%	$40.9715	$40.97	$40.95	$41.00
Purchase #6	$224.38	11.531%	$250.2533	$250.25	$250.25	$250.30
Purchase #7	$55.91	13.727%	$63.5848	$63.58	$63.60	$63.60
7 purchase totals =	$930.02		$1,025.4716	$1,025.47	$1,025.50	$1,025.50