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	$55.82	13.856%	$63.5544	$63.55	$63.55	$63.60
Purchase #2	$204.89	12.150%	$229.7841	$229.78	$229.80	$229.80
Purchase #3	$94.72	11.215%	$105.3428	$105.34	$105.35	$105.30
Purchase #4	$152.44	5.246%	$160.437	$160.44	$160.45	$160.40
Purchase #5	$70.65	13.146%	$79.9376	$79.94	$79.95	$79.90
Purchase #6	$212.73	12.320%	$238.9383	$238.94	$238.95	$238.90
Purchase #7	$162.63	12.721%	$183.3182	$183.32	$183.30	$183.30
7 purchase totals =	$953.88		$1,061.3124	$1,061.31	$1,061.35	$1,061.20