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	$54.50	10.754%	$60.3609	$60.36	$60.35	$60.40
Purchase #2	$162.35	11.334%	$180.7507	$180.75	$180.75	$180.80
Purchase #3	$180.59	5.649%	$190.7915	$190.79	$190.80	$190.80
Purchase #4	$162.31	6.865%	$173.4526	$173.45	$173.45	$173.50
Purchase #5	$200.67	3.118%	$206.9269	$206.93	$206.95	$206.90
Purchase #6	$126.35	12.647%	$142.3295	$142.33	$142.35	$142.30
Purchase #7	$234.29	3.347%	$242.1317	$242.13	$242.15	$242.10
7 purchase totals =	$1,121.06		$1,196.7438	$1,196.74	$1,196.80	$1,196.80