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	$174.77	5.594%	$184.5466	$184.55	$184.55	$184.50
Purchase #2	$137.74	13.474%	$156.2991	$156.30	$156.30	$156.30
Purchase #3	$36.33	6.223%	$38.5908	$38.59	$38.60	$38.60
Purchase #4	$140.46	13.725%	$159.7381	$159.74	$159.75	$159.70
Purchase #5	$201.31	13.231%	$227.9453	$227.95	$227.95	$227.90
Purchase #6	$164.90	10.667%	$182.4899	$182.49	$182.50	$182.50
Purchase #7	$129.43	11.862%	$144.783	$144.78	$144.80	$144.80
7 purchase totals =	$984.94		$1,094.3928	$1,094.40	$1,094.45	$1,094.30