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	$98.78	6.782%	$105.4793	$105.48	$105.50	$105.50
Purchase #2	$178.66	9.728%	$196.04	$196.04	$196.05	$196.00
Purchase #3	$211.34	11.567%	$235.7857	$235.79	$235.80	$235.80
Purchase #4	$153.87	4.451%	$160.7188	$160.72	$160.70	$160.70
Purchase #5	$71.66	12.216%	$80.414	$80.41	$80.40	$80.40
Purchase #6	$205.34	12.301%	$230.5989	$230.60	$230.60	$230.60
Purchase #7	$54.25	6.509%	$57.7811	$57.78	$57.80	$57.80
7 purchase totals =	$973.90		$1,066.8178	$1,066.82	$1,066.85	$1,066.80