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	$64.47	11.712%	$72.0207	$72.02	$72.00	$72.00
Purchase #2	$200.76	4.430%	$209.6537	$209.65	$209.65	$209.70
Purchase #3	$76.91	11.816%	$85.9977	$86.00	$86.00	$86.00
Purchase #4	$42.55	13.658%	$48.3615	$48.36	$48.35	$48.40
Purchase #5	$114.60	10.831%	$127.0123	$127.01	$127.00	$127.00
Purchase #6	$14.86	3.470%	$15.3756	$15.38	$15.40	$15.40
Purchase #7	$114.70	13.860%	$130.5974	$130.60	$130.60	$130.60
7 purchase totals =	$628.85		$689.0189	$689.02	$689.00	$689.10