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	$76.58	7.635%	$82.4269	$82.43	$82.45	$82.40
Purchase #2	$243.92	12.553%	$274.5393	$274.54	$274.55	$274.50
Purchase #3	$44.28	7.220%	$47.477	$47.48	$47.50	$47.50
Purchase #4	$221.71	9.177%	$242.0563	$242.06	$242.05	$242.10
Purchase #5	$51.48	7.305%	$55.2406	$55.24	$55.25	$55.20
Purchase #6	$39.43	3.128%	$40.6634	$40.66	$40.65	$40.70
Purchase #7	$5.98	8.538%	$6.4906	$6.49	$6.50	$6.50
7 purchase totals =	$683.38		$748.8941	$748.90	$748.95	$748.90