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	$80.45	7.298%	$86.3212	$86.32	$86.30	$86.30
Purchase #2	$215.41	3.857%	$223.7184	$223.72	$223.70	$223.70
Purchase #3	$204.88	12.562%	$230.617	$230.62	$230.60	$230.60
Purchase #4	$55.49	4.545%	$58.012	$58.01	$58.00	$58.00
Purchase #5	$70.70	10.476%	$78.1065	$78.11	$78.10	$78.10
Purchase #6	$183.92	9.204%	$200.848	$200.85	$200.85	$200.80
Purchase #7	$188.64	9.637%	$206.8192	$206.82	$206.80	$206.80
7 purchase totals =	$999.49		$1,084.4423	$1,084.45	$1,084.35	$1,084.30