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	$246.76	8.131%	$266.8241	$266.82	$266.80	$266.80
Purchase #2	$117.40	7.678%	$126.414	$126.41	$126.40	$126.40
Purchase #3	$49.83	12.176%	$55.8973	$55.90	$55.90	$55.90
Purchase #4	$79.57	12.151%	$89.2386	$89.24	$89.25	$89.20
Purchase #5	$231.61	8.236%	$250.6854	$250.69	$250.70	$250.70
Purchase #6	$101.33	3.153%	$104.5249	$104.52	$104.50	$104.50
Purchase #7	$127.36	5.463%	$134.3177	$134.32	$134.30	$134.30
7 purchase totals =	$953.86		$1,027.9020	$1,027.90	$1,027.85	$1,027.80