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	$15.48	10.720%	$17.1395	$17.14	$17.15	$17.10
Purchase #2	$47.33	6.600%	$50.4538	$50.45	$50.45	$50.50
Purchase #3	$113.69	12.698%	$128.1264	$128.13	$128.15	$128.10
Purchase #4	$96.33	6.168%	$102.2716	$102.27	$102.25	$102.30
Purchase #5	$159.54	4.248%	$166.3173	$166.32	$166.30	$166.30
Purchase #6	$117.76	5.725%	$124.5018	$124.50	$124.50	$124.50
Purchase #7	$128.67	12.161%	$144.3176	$144.32	$144.30	$144.30
7 purchase totals =	$678.80		$733.1280	$733.13	$733.10	$733.10