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	$97.92	5.578%	$103.382	$103.38	$103.40	$103.40
Purchase #2	$23.33	9.589%	$25.5671	$25.57	$25.55	$25.60
Purchase #3	$130.73	9.716%	$143.4317	$143.43	$143.45	$143.40
Purchase #4	$87.55	13.655%	$99.505	$99.51	$99.50	$99.50
Purchase #5	$182.50	4.288%	$190.3256	$190.33	$190.35	$190.30
Purchase #6	$67.90	12.748%	$76.5559	$76.56	$76.55	$76.60
Purchase #7	$169.44	11.425%	$188.7985	$188.80	$188.80	$188.80
7 purchase totals =	$759.37		$827.5658	$827.58	$827.60	$827.60