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	$171.62	13.297%	$194.4403	$194.44	$194.45	$194.40
Purchase #2	$79.28	3.553%	$82.0968	$82.10	$82.10	$82.10
Purchase #3	$146.34	10.793%	$162.1345	$162.13	$162.15	$162.10
Purchase #4	$237.31	6.821%	$253.4969	$253.50	$253.50	$253.50
Purchase #5	$181.48	4.864%	$190.3072	$190.31	$190.30	$190.30
Purchase #6	$233.48	3.173%	$240.8883	$240.89	$240.90	$240.90
Purchase #7	$231.29	12.747%	$260.7725	$260.77	$260.75	$260.80
7 purchase totals =	$1,280.80		$1,384.1365	$1,384.14	$1,384.15	$1,384.10