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	$151.55	11.774%	$169.3935	$169.39	$169.40	$169.40
Purchase #2	$29.81	9.298%	$32.5817	$32.58	$32.60	$32.60
Purchase #3	$183.86	13.472%	$208.6296	$208.63	$208.65	$208.60
Purchase #4	$213.31	9.342%	$233.2374	$233.24	$233.25	$233.20
Purchase #5	$131.40	9.425%	$143.7845	$143.78	$143.80	$143.80
Purchase #6	$209.78	9.381%	$229.4595	$229.46	$229.45	$229.50
Purchase #7	$126.27	12.805%	$142.4389	$142.44	$142.45	$142.40
7 purchase totals =	$1,045.98		$1,159.5251	$1,159.52	$1,159.60	$1,159.50