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	$233.65	3.718%	$242.3371	$242.34	$242.35	$242.30
Purchase #2	$212.33	10.333%	$234.2701	$234.27	$234.25	$234.30
Purchase #3	$34.58	4.153%	$36.0161	$36.02	$36.00	$36.00
Purchase #4	$138.33	10.297%	$152.5738	$152.57	$152.55	$152.60
Purchase #5	$40.85	11.379%	$45.4983	$45.50	$45.50	$45.50
Purchase #6	$73.85	9.183%	$80.6316	$80.63	$80.65	$80.60
Purchase #7	$241.42	12.390%	$271.3319	$271.33	$271.35	$271.30
7 purchase totals =	$975.01		$1,062.6589	$1,062.66	$1,062.65	$1,062.60