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	$159.44	7.575%	$171.5176	$171.52	$171.50	$171.50
Purchase #2	$30.36	4.856%	$31.8343	$31.83	$31.85	$31.80
Purchase #3	$10.26	11.205%	$11.4096	$11.41	$11.40	$11.40
Purchase #4	$144.79	12.454%	$162.8221	$162.82	$162.80	$162.80
Purchase #5	$42.66	11.577%	$47.5987	$47.60	$47.60	$47.60
Purchase #6	$42.88	7.589%	$46.1342	$46.13	$46.15	$46.10
Purchase #7	$143.26	9.360%	$156.6691	$156.67	$156.65	$156.70
7 purchase totals =	$573.65		$627.9856	$627.98	$627.95	$627.90