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	$59.60	12.673%	$67.1531	$67.15	$67.15	$67.20
Purchase #2	$25.66	6.655%	$27.3677	$27.37	$27.35	$27.40
Purchase #3	$62.29	11.145%	$69.2322	$69.23	$69.25	$69.20
Purchase #4	$5.92	7.249%	$6.3491	$6.35	$6.35	$6.30
Purchase #5	$137.69	11.807%	$153.9471	$153.95	$153.95	$153.90
Purchase #6	$89.31	7.402%	$95.9207	$95.92	$95.90	$95.90
Purchase #7	$72.99	7.353%	$78.357	$78.36	$78.35	$78.40
7 purchase totals =	$453.46		$498.3269	$498.33	$498.30	$498.30