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	$82.84	4.162%	$86.2878	$86.29	$86.30	$86.30
Purchase #2	$174.33	4.872%	$182.8234	$182.82	$182.80	$182.80
Purchase #3	$233.70	7.358%	$250.8956	$250.90	$250.90	$250.90
Purchase #4	$121.90	8.766%	$132.5858	$132.59	$132.60	$132.60
Purchase #5	$203.98	4.154%	$212.4533	$212.45	$212.45	$212.50
Purchase #6	$100.79	12.761%	$113.6518	$113.65	$113.65	$113.70
Purchase #7	$47.89	5.673%	$50.6068	$50.61	$50.60	$50.60
7 purchase totals =	$965.43		$1,029.3045	$1,029.31	$1,029.30	$1,029.40