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	$233.80	4.791%	$245.0014	$245.00	$245.00	$245.00
Purchase #2	$217.89	3.176%	$224.8102	$224.81	$224.80	$224.80
Purchase #3	$118.97	11.409%	$132.5433	$132.54	$132.55	$132.50
Purchase #4	$247.68	6.220%	$263.0857	$263.09	$263.10	$263.10
Purchase #5	$56.36	5.419%	$59.4141	$59.41	$59.40	$59.40
Purchase #6	$168.43	3.402%	$174.16	$174.16	$174.15	$174.20
Purchase #7	$37.38	13.264%	$42.3381	$42.34	$42.35	$42.30
7 purchase totals =	$1,080.51		$1,141.3528	$1,141.35	$1,141.35	$1,141.30