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	$129.81	4.585%	$135.7618	$135.76	$135.75	$135.80
Purchase #2	$94.35	11.866%	$105.5456	$105.55	$105.55	$105.50
Purchase #3	$188.87	3.779%	$196.0074	$196.01	$196.00	$196.00
Purchase #4	$25.35	11.398%	$28.2394	$28.24	$28.25	$28.20
Purchase #5	$245.83	13.270%	$278.4516	$278.45	$278.45	$278.50
Purchase #6	$147.78	4.102%	$153.8419	$153.84	$153.85	$153.80
Purchase #7	$85.39	13.784%	$97.1602	$97.16	$97.15	$97.20
7 purchase totals =	$917.38		$995.0079	$995.01	$995.00	$995.00