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	$218.60	10.601%	$241.7738	$241.77	$241.75	$241.80
Purchase #2	$219.34	5.488%	$231.3774	$231.38	$231.40	$231.40
Purchase #3	$62.88	7.814%	$67.7934	$67.79	$67.80	$67.80
Purchase #4	$99.85	11.769%	$111.6013	$111.60	$111.60	$111.60
Purchase #5	$247.70	8.305%	$268.2715	$268.27	$268.25	$268.30
Purchase #6	$81.89	8.466%	$88.8228	$88.82	$88.80	$88.80
Purchase #7	$210.95	10.664%	$233.4457	$233.45	$233.45	$233.40
7 purchase totals =	$1,141.21		$1,243.0859	$1,243.08	$1,243.05	$1,243.10