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	$241.66	10.654%	$267.4065	$267.41	$267.40	$267.40
Purchase #2	$115.64	11.461%	$128.8935	$128.89	$128.90	$128.90
Purchase #3	$207.27	11.818%	$231.7652	$231.77	$231.75	$231.80
Purchase #4	$81.71	9.213%	$89.2379	$89.24	$89.25	$89.20
Purchase #5	$150.27	9.181%	$164.0663	$164.07	$164.05	$164.10
Purchase #6	$182.94	7.648%	$196.9313	$196.93	$196.95	$196.90
Purchase #7	$35.40	6.845%	$37.8231	$37.82	$37.80	$37.80
7 purchase totals =	$1,014.89		$1,116.1238	$1,116.13	$1,116.10	$1,116.10