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	$59.72	11.365%	$66.5072	$66.51	$66.50	$66.50
Purchase #2	$136.50	11.475%	$152.1634	$152.16	$152.15	$152.20
Purchase #3	$208.78	6.740%	$222.8518	$222.85	$222.85	$222.90
Purchase #4	$42.27	5.631%	$44.6502	$44.65	$44.65	$44.70
Purchase #5	$234.86	13.574%	$266.7399	$266.74	$266.75	$266.70
Purchase #6	$118.73	10.446%	$131.1325	$131.13	$131.15	$131.10
Purchase #7	$186.42	9.632%	$204.376	$204.38	$204.40	$204.40
7 purchase totals =	$987.28		$1,088.4210	$1,088.42	$1,088.45	$1,088.50