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	$147.42	11.447%	$164.2952	$164.30	$164.30	$164.30
Purchase #2	$164.83	11.860%	$184.3788	$184.38	$184.40	$184.40
Purchase #3	$50.98	13.103%	$57.6599	$57.66	$57.65	$57.70
Purchase #4	$188.57	11.845%	$210.9061	$210.91	$210.90	$210.90
Purchase #5	$197.37	9.874%	$216.8583	$216.86	$216.85	$216.90
Purchase #6	$127.81	3.700%	$132.539	$132.54	$132.55	$132.50
Purchase #7	$134.45	3.199%	$138.7511	$138.75	$138.75	$138.80
7 purchase totals =	$1,011.43		$1,105.3884	$1,105.40	$1,105.40	$1,105.50