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	$240.80	10.111%	$265.1473	$265.15	$265.15	$265.10
Purchase #2	$215.70	8.409%	$233.8382	$233.84	$233.85	$233.80
Purchase #3	$210.99	9.146%	$230.2871	$230.29	$230.30	$230.30
Purchase #4	$59.51	5.721%	$62.9146	$62.91	$62.90	$62.90
Purchase #5	$143.78	8.546%	$156.0674	$156.07	$156.05	$156.10
Purchase #6	$158.84	6.220%	$168.7198	$168.72	$168.70	$168.70
Purchase #7	$128.30	8.700%	$139.4621	$139.46	$139.45	$139.50
7 purchase totals =	$1,157.92		$1,256.4365	$1,256.44	$1,256.40	$1,256.40