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	$78.31	5.478%	$82.5998	$82.60	$82.60	$82.60
Purchase #2	$184.96	11.466%	$206.1675	$206.17	$206.15	$206.20
Purchase #3	$160.81	13.730%	$182.8892	$182.89	$182.90	$182.90
Purchase #4	$8.49	3.160%	$8.7583	$8.76	$8.75	$8.80
Purchase #5	$244.36	4.600%	$255.6006	$255.60	$255.60	$255.60
Purchase #6	$205.48	13.630%	$233.4869	$233.49	$233.50	$233.50
Purchase #7	$146.75	6.372%	$156.1009	$156.10	$156.10	$156.10
7 purchase totals =	$1,029.16		$1,125.6032	$1,125.61	$1,125.60	$1,125.70