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	$123.90	6.229%	$131.6177	$131.62	$131.60	$131.60
Purchase #2	$194.69	11.523%	$217.1241	$217.12	$217.10	$217.10
Purchase #3	$185.79	6.542%	$197.9444	$197.94	$197.95	$197.90
Purchase #4	$55.93	5.870%	$59.2131	$59.21	$59.20	$59.20
Purchase #5	$224.30	8.155%	$242.5917	$242.59	$242.60	$242.60
Purchase #6	$30.42	11.710%	$33.9822	$33.98	$34.00	$34.00
Purchase #7	$164.93	3.648%	$170.9466	$170.95	$170.95	$170.90
7 purchase totals =	$979.96		$1,053.4198	$1,053.41	$1,053.40	$1,053.30