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	$89.62	3.151%	$92.4439	$92.44	$92.45	$92.40
Purchase #2	$69.53	4.651%	$72.7638	$72.76	$72.75	$72.80
Purchase #3	$127.43	10.333%	$140.5973	$140.60	$140.60	$140.60
Purchase #4	$134.69	8.463%	$146.0888	$146.09	$146.10	$146.10
Purchase #5	$111.25	8.434%	$120.6328	$120.63	$120.65	$120.60
Purchase #6	$99.83	4.289%	$104.1117	$104.11	$104.10	$104.10
Purchase #7	$144.66	10.143%	$159.3329	$159.33	$159.35	$159.30
7 purchase totals =	$777.01		$835.9712	$835.96	$836.00	$835.90