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	$212.54	9.123%	$231.93	$231.93	$231.95	$231.90
Purchase #2	$103.63	5.519%	$109.3493	$109.35	$109.35	$109.30
Purchase #3	$183.71	8.823%	$199.9187	$199.92	$199.90	$199.90
Purchase #4	$244.52	4.555%	$255.6579	$255.66	$255.65	$255.70
Purchase #5	$114.94	4.795%	$120.4514	$120.45	$120.45	$120.50
Purchase #6	$230.44	10.331%	$254.2468	$254.25	$254.25	$254.20
Purchase #7	$148.75	9.165%	$162.3829	$162.38	$162.40	$162.40
7 purchase totals =	$1,238.53		$1,333.9370	$1,333.94	$1,333.95	$1,333.90