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	$65.82	10.283%	$72.5883	$72.59	$72.60	$72.60
Purchase #2	$99.28	10.414%	$109.619	$109.62	$109.60	$109.60
Purchase #3	$24.96	5.566%	$26.3493	$26.35	$26.35	$26.30
Purchase #4	$217.94	5.257%	$229.3971	$229.40	$229.40	$229.40
Purchase #5	$178.80	8.643%	$194.2537	$194.25	$194.25	$194.30
Purchase #6	$131.34	10.663%	$145.3448	$145.34	$145.35	$145.30
Purchase #7	$148.82	12.159%	$166.915	$166.92	$166.90	$166.90
7 purchase totals =	$866.96		$944.4672	$944.47	$944.45	$944.40