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	$206.90	11.168%	$230.0066	$230.01	$230.00	$230.00
Purchase #2	$98.46	5.777%	$104.148	$104.15	$104.15	$104.10
Purchase #3	$186.64	4.179%	$194.4397	$194.44	$194.45	$194.40
Purchase #4	$69.30	13.336%	$78.5418	$78.54	$78.55	$78.50
Purchase #5	$250.34	4.809%	$262.3789	$262.38	$262.40	$262.40
Purchase #6	$186.33	4.414%	$194.5546	$194.55	$194.55	$194.60
Purchase #7	$160.45	3.754%	$166.4733	$166.47	$166.45	$166.50
7 purchase totals =	$1,158.42		$1,230.5429	$1,230.54	$1,230.55	$1,230.50