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	$177.33	12.330%	$199.1948	$199.19	$199.20	$199.20
Purchase #2	$150.27	12.827%	$169.5451	$169.55	$169.55	$169.50
Purchase #3	$63.67	4.324%	$66.4231	$66.42	$66.40	$66.40
Purchase #4	$9.95	5.488%	$10.4961	$10.50	$10.50	$10.50
Purchase #5	$98.82	6.151%	$104.8984	$104.90	$104.90	$104.90
Purchase #6	$159.59	8.276%	$172.7977	$172.80	$172.80	$172.80
Purchase #7	$104.55	4.631%	$109.3917	$109.39	$109.40	$109.40
7 purchase totals =	$764.18		$832.7469	$832.75	$832.75	$832.70