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	$168.68	8.687%	$183.3332	$183.33	$183.35	$183.30
Purchase #2	$150.54	11.856%	$168.388	$168.39	$168.40	$168.40
Purchase #3	$109.54	4.477%	$114.4441	$114.44	$114.45	$114.40
Purchase #4	$132.34	9.834%	$145.3543	$145.35	$145.35	$145.40
Purchase #5	$89.32	7.439%	$95.9645	$95.96	$95.95	$96.00
Purchase #6	$109.89	9.861%	$120.7263	$120.73	$120.75	$120.70
Purchase #7	$127.91	8.245%	$138.4562	$138.46	$138.45	$138.50
7 purchase totals =	$888.22		$966.6666	$966.66	$966.70	$966.70