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	$150.81	5.352%	$158.8814	$158.88	$158.90	$158.90
Purchase #2	$137.44	11.588%	$153.3665	$153.37	$153.35	$153.40
Purchase #3	$214.62	13.760%	$244.1517	$244.15	$244.15	$244.20
Purchase #4	$142.66	5.758%	$150.8744	$150.87	$150.85	$150.90
Purchase #5	$90.29	13.524%	$102.5008	$102.50	$102.50	$102.50
Purchase #6	$182.31	5.732%	$192.76	$192.76	$192.75	$192.80
Purchase #7	$222.93	12.494%	$250.7829	$250.78	$250.80	$250.80
7 purchase totals =	$1,141.06		$1,253.3177	$1,253.31	$1,253.30	$1,253.50