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	$181.79	11.610%	$202.8958	$202.90	$202.90	$202.90
Purchase #2	$19.56	11.192%	$21.7492	$21.75	$21.75	$21.70
Purchase #3	$60.56	12.723%	$68.265	$68.27	$68.25	$68.30
Purchase #4	$93.31	13.571%	$105.9731	$105.97	$105.95	$106.00
Purchase #5	$170.97	11.470%	$190.5803	$190.58	$190.60	$190.60
Purchase #6	$64.83	11.730%	$72.4346	$72.43	$72.45	$72.40
Purchase #7	$100.90	4.413%	$105.3527	$105.35	$105.35	$105.40
7 purchase totals =	$691.92		$767.2507	$767.25	$767.25	$767.30