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	$73.81	12.585%	$83.099	$83.10	$83.10	$83.10
Purchase #2	$158.72	9.130%	$173.2111	$173.21	$173.20	$173.20
Purchase #3	$196.65	7.329%	$211.0625	$211.06	$211.05	$211.10
Purchase #4	$86.71	9.142%	$94.637	$94.64	$94.65	$94.60
Purchase #5	$33.98	10.566%	$37.5703	$37.57	$37.55	$37.60
Purchase #6	$38.40	12.410%	$43.1654	$43.17	$43.15	$43.20
Purchase #7	$113.50	4.809%	$118.9582	$118.96	$118.95	$119.00
7 purchase totals =	$701.77		$761.7035	$761.71	$761.65	$761.80