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	$86.46	13.391%	$98.0379	$98.04	$98.05	$98.00
Purchase #2	$34.60	8.293%	$37.4694	$37.47	$37.45	$37.50
Purchase #3	$103.28	5.470%	$108.9294	$108.93	$108.95	$108.90
Purchase #4	$250.33	8.141%	$270.7094	$270.71	$270.70	$270.70
Purchase #5	$175.39	5.236%	$184.5734	$184.57	$184.55	$184.60
Purchase #6	$196.68	12.772%	$221.8	$221.80	$221.80	$221.80
Purchase #7	$73.59	12.485%	$82.7777	$82.78	$82.80	$82.80
7 purchase totals =	$920.33		$1,004.2972	$1,004.30	$1,004.30	$1,004.30