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	$175.66	13.860%	$200.0065	$200.01	$200.00	$200.00
Purchase #2	$120.71	9.702%	$132.4213	$132.42	$132.40	$132.40
Purchase #3	$114.85	12.686%	$129.4199	$129.42	$129.40	$129.40
Purchase #4	$178.47	5.637%	$188.5304	$188.53	$188.55	$188.50
Purchase #5	$75.75	9.423%	$82.8879	$82.89	$82.90	$82.90
Purchase #6	$76.52	13.458%	$86.8181	$86.82	$86.80	$86.80
Purchase #7	$93.64	11.510%	$104.418	$104.42	$104.40	$104.40
7 purchase totals =	$835.60		$924.5021	$924.51	$924.45	$924.40