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	$211.99	4.266%	$221.0335	$221.03	$221.05	$221.00
Purchase #2	$181.54	3.759%	$188.3641	$188.36	$188.35	$188.40
Purchase #3	$68.36	13.244%	$77.4136	$77.41	$77.40	$77.40
Purchase #4	$119.75	7.317%	$128.5121	$128.51	$128.50	$128.50
Purchase #5	$169.66	11.797%	$189.6748	$189.67	$189.65	$189.70
Purchase #6	$45.99	12.182%	$51.5925	$51.59	$51.60	$51.60
Purchase #7	$138.54	4.587%	$144.8948	$144.89	$144.90	$144.90
7 purchase totals =	$935.83		$1,001.4854	$1,001.46	$1,001.45	$1,001.50