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	$39.52	12.341%	$44.3972	$44.40	$44.40	$44.40
Purchase #2	$81.82	11.158%	$90.9495	$90.95	$90.95	$90.90
Purchase #3	$163.66	13.548%	$185.8327	$185.83	$185.85	$185.80
Purchase #4	$143.95	11.333%	$160.2639	$160.26	$160.25	$160.30
Purchase #5	$135.41	4.686%	$141.7553	$141.76	$141.75	$141.80
Purchase #6	$159.40	5.708%	$168.4986	$168.50	$168.50	$168.50
Purchase #7	$233.75	5.182%	$245.8629	$245.86	$245.85	$245.90
7 purchase totals =	$957.51		$1,037.5601	$1,037.56	$1,037.55	$1,037.60