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	$48.44	11.853%	$54.1816	$54.18	$54.20	$54.20
Purchase #2	$144.41	10.640%	$159.7752	$159.78	$159.80	$159.80
Purchase #3	$145.57	12.677%	$164.0239	$164.02	$164.00	$164.00
Purchase #4	$190.91	11.168%	$212.2308	$212.23	$212.25	$212.20
Purchase #5	$182.59	11.182%	$203.0072	$203.01	$203.00	$203.00
Purchase #6	$236.26	6.617%	$251.8933	$251.89	$251.90	$251.90
Purchase #7	$110.48	11.740%	$123.4504	$123.45	$123.45	$123.50
7 purchase totals =	$1,058.66		$1,168.5624	$1,168.56	$1,168.60	$1,168.60