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	$84.37	8.132%	$91.231	$91.23	$91.25	$91.20
Purchase #2	$73.45	4.176%	$76.5173	$76.52	$76.50	$76.50
Purchase #3	$92.94	7.683%	$100.0806	$100.08	$100.10	$100.10
Purchase #4	$37.93	11.530%	$42.3033	$42.30	$42.30	$42.30
Purchase #5	$82.55	4.409%	$86.1896	$86.19	$86.20	$86.20
Purchase #6	$166.40	8.844%	$181.1164	$181.12	$181.10	$181.10
Purchase #7	$195.27	5.392%	$205.799	$205.80	$205.80	$205.80
7 purchase totals =	$732.91		$783.2372	$783.24	$783.25	$783.20