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	$188.37	13.856%	$214.4705	$214.47	$214.45	$214.50
Purchase #2	$81.36	8.486%	$88.2642	$88.26	$88.25	$88.30
Purchase #3	$73.83	11.140%	$82.0547	$82.05	$82.05	$82.10
Purchase #4	$71.77	6.469%	$76.4128	$76.41	$76.40	$76.40
Purchase #5	$55.43	9.316%	$60.5939	$60.59	$60.60	$60.60
Purchase #6	$42.81	6.452%	$45.5721	$45.57	$45.55	$45.60
Purchase #7	$82.65	7.456%	$88.8124	$88.81	$88.80	$88.80
7 purchase totals =	$596.22		$656.1806	$656.16	$656.10	$656.30