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	$143.64	6.153%	$152.4782	$152.48	$152.50	$152.50
Purchase #2	$127.66	6.776%	$136.3102	$136.31	$136.30	$136.30
Purchase #3	$73.49	6.399%	$78.1926	$78.19	$78.20	$78.20
Purchase #4	$166.58	12.254%	$186.9927	$186.99	$187.00	$187.00
Purchase #5	$229.53	11.377%	$255.6436	$255.64	$255.65	$255.60
Purchase #6	$50.96	12.787%	$57.4763	$57.48	$57.50	$57.50
Purchase #7	$76.97	12.535%	$86.6182	$86.62	$86.60	$86.60
7 purchase totals =	$868.83		$953.7118	$953.71	$953.75	$953.70