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	$31.59	3.645%	$32.7415	$32.74	$32.75	$32.70
Purchase #2	$203.73	9.477%	$223.0375	$223.04	$223.05	$223.00
Purchase #3	$146.46	5.294%	$154.2136	$154.21	$154.20	$154.20
Purchase #4	$147.46	5.751%	$155.9404	$155.94	$155.95	$155.90
Purchase #5	$222.52	10.134%	$245.0702	$245.07	$245.05	$245.10
Purchase #6	$217.38	11.570%	$242.5309	$242.53	$242.55	$242.50
Purchase #7	$39.75	9.556%	$43.5485	$43.55	$43.55	$43.50
7 purchase totals =	$1,008.89		$1,097.0826	$1,097.08	$1,097.10	$1,096.90