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	$109.67	6.267%	$116.543	$116.54	$116.55	$116.50
Purchase #2	$63.91	12.352%	$71.8042	$71.80	$71.80	$71.80
Purchase #3	$61.62	7.692%	$66.3598	$66.36	$66.35	$66.40
Purchase #4	$86.90	4.579%	$90.8792	$90.88	$90.90	$90.90
Purchase #5	$16.74	8.229%	$18.1175	$18.12	$18.10	$18.10
Purchase #6	$100.33	10.551%	$110.9158	$110.92	$110.90	$110.90
Purchase #7	$175.76	7.221%	$188.4516	$188.45	$188.45	$188.50
7 purchase totals =	$614.93		$663.0711	$663.07	$663.05	$663.10