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	$189.50	3.492%	$196.1173	$196.12	$196.10	$196.10
Purchase #2	$234.53	12.453%	$263.736	$263.74	$263.75	$263.70
Purchase #3	$216.71	7.759%	$233.5245	$233.52	$233.50	$233.50
Purchase #4	$111.46	13.627%	$126.6487	$126.65	$126.65	$126.60
Purchase #5	$176.37	3.830%	$183.125	$183.13	$183.15	$183.10
Purchase #6	$44.59	9.466%	$48.8109	$48.81	$48.80	$48.80
Purchase #7	$223.71	13.772%	$254.5193	$254.52	$254.50	$254.50
7 purchase totals =	$1,196.87		$1,306.4817	$1,306.49	$1,306.45	$1,306.30