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	$230.89	8.428%	$250.3494	$250.35	$250.35	$250.30
Purchase #2	$93.27	7.833%	$100.5758	$100.58	$100.60	$100.60
Purchase #3	$104.44	12.874%	$117.8856	$117.89	$117.90	$117.90
Purchase #4	$26.43	3.791%	$27.432	$27.43	$27.45	$27.40
Purchase #5	$177.69	12.336%	$199.6098	$199.61	$199.60	$199.60
Purchase #6	$216.58	3.179%	$223.4651	$223.47	$223.45	$223.50
Purchase #7	$250.76	12.713%	$282.6391	$282.64	$282.65	$282.60
7 purchase totals =	$1,100.06		$1,201.9568	$1,201.97	$1,202.00	$1,201.90