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	$91.76	13.130%	$103.8081	$103.81	$103.80	$103.80
Purchase #2	$41.71	11.215%	$46.3878	$46.39	$46.40	$46.40
Purchase #3	$8.25	12.835%	$9.3089	$9.31	$9.30	$9.30
Purchase #4	$102.55	6.729%	$109.4506	$109.45	$109.45	$109.50
Purchase #5	$98.96	13.537%	$112.3562	$112.36	$112.35	$112.40
Purchase #6	$165.28	10.718%	$182.9947	$182.99	$183.00	$183.00
Purchase #7	$59.52	3.517%	$61.6133	$61.61	$61.60	$61.60
7 purchase totals =	$568.03		$625.9196	$625.92	$625.90	$626.00