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	$52.40	12.622%	$59.0139	$59.01	$59.00	$59.00
Purchase #2	$232.55	9.442%	$254.5074	$254.51	$254.50	$254.50
Purchase #3	$74.97	10.565%	$82.8906	$82.89	$82.90	$82.90
Purchase #4	$151.74	8.530%	$164.6834	$164.68	$164.70	$164.70
Purchase #5	$169.92	10.559%	$187.8619	$187.86	$187.85	$187.90
Purchase #6	$41.76	6.144%	$44.3257	$44.33	$44.35	$44.30
Purchase #7	$214.95	8.611%	$233.4593	$233.46	$233.45	$233.50
7 purchase totals =	$938.29		$1,026.7422	$1,026.74	$1,026.75	$1,026.80