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	$206.33	13.499%	$234.1825	$234.18	$234.20	$234.20
Purchase #2	$61.38	10.112%	$67.5867	$67.59	$67.60	$67.60
Purchase #3	$193.87	9.845%	$212.9565	$212.96	$212.95	$213.00
Purchase #4	$125.82	6.717%	$134.2713	$134.27	$134.25	$134.30
Purchase #5	$233.56	3.446%	$241.6085	$241.61	$241.60	$241.60
Purchase #6	$160.78	8.461%	$174.3836	$174.38	$174.40	$174.40
Purchase #7	$34.32	12.145%	$38.4882	$38.49	$38.50	$38.50
7 purchase totals =	$1,016.06		$1,103.4773	$1,103.48	$1,103.50	$1,103.60