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	$175.89	9.710%	$192.9689	$192.97	$192.95	$193.00
Purchase #2	$103.42	12.636%	$116.4882	$116.49	$116.50	$116.50
Purchase #3	$46.30	12.127%	$51.9148	$51.91	$51.90	$51.90
Purchase #4	$13.53	4.678%	$14.1629	$14.16	$14.15	$14.20
Purchase #5	$63.82	11.463%	$71.1357	$71.14	$71.15	$71.10
Purchase #6	$157.50	6.828%	$168.2541	$168.25	$168.25	$168.30
Purchase #7	$71.42	7.486%	$76.7665	$76.77	$76.75	$76.80
7 purchase totals =	$631.88		$691.6911	$691.69	$691.65	$691.80