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	$52.64	4.277%	$54.8914	$54.89	$54.90	$54.90
Purchase #2	$82.83	9.331%	$90.5589	$90.56	$90.55	$90.60
Purchase #3	$84.26	8.482%	$91.4069	$91.41	$91.40	$91.40
Purchase #4	$192.94	5.220%	$203.0115	$203.01	$203.00	$203.00
Purchase #5	$221.49	5.476%	$233.6188	$233.62	$233.60	$233.60
Purchase #6	$127.67	11.537%	$142.3993	$142.40	$142.40	$142.40
Purchase #7	$210.64	3.336%	$217.667	$217.67	$217.65	$217.70
7 purchase totals =	$972.47		$1,033.5538	$1,033.56	$1,033.50	$1,033.60