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	$148.43	13.321%	$168.2024	$168.20	$168.20	$168.20
Purchase #2	$85.84	5.751%	$90.7767	$90.78	$90.80	$90.80
Purchase #3	$143.58	7.757%	$154.7175	$154.72	$154.70	$154.70
Purchase #4	$242.89	11.453%	$270.7082	$270.71	$270.70	$270.70
Purchase #5	$151.67	8.200%	$164.1069	$164.11	$164.10	$164.10
Purchase #6	$78.89	3.766%	$81.861	$81.86	$81.85	$81.90
Purchase #7	$206.87	3.717%	$214.5594	$214.56	$214.55	$214.60
7 purchase totals =	$1,058.17		$1,144.9321	$1,144.94	$1,144.90	$1,145.00