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	$132.94	8.334%	$144.0192	$144.02	$144.00	$144.00
Purchase #2	$142.99	7.334%	$153.4769	$153.48	$153.50	$153.50
Purchase #3	$58.64	4.354%	$61.1932	$61.19	$61.20	$61.20
Purchase #4	$184.34	6.664%	$196.6244	$196.62	$196.60	$196.60
Purchase #5	$245.34	10.224%	$270.4236	$270.42	$270.40	$270.40
Purchase #6	$246.74	12.332%	$277.168	$277.17	$277.15	$277.20
Purchase #7	$229.33	11.393%	$255.4576	$255.46	$255.45	$255.50
7 purchase totals =	$1,240.32		$1,358.3629	$1,358.36	$1,358.30	$1,358.40