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	$195.55	9.107%	$213.3587	$213.36	$213.35	$213.40
Purchase #2	$77.54	11.124%	$86.1655	$86.17	$86.15	$86.20
Purchase #3	$113.42	9.177%	$123.8286	$123.83	$123.85	$123.80
Purchase #4	$85.82	12.296%	$96.3724	$96.37	$96.35	$96.40
Purchase #5	$30.61	6.740%	$32.6731	$32.67	$32.65	$32.70
Purchase #6	$111.74	10.785%	$123.7912	$123.79	$123.80	$123.80
Purchase #7	$201.82	7.153%	$216.2562	$216.26	$216.25	$216.30
7 purchase totals =	$816.50		$892.4457	$892.45	$892.40	$892.60