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	$161.53	10.265%	$178.1111	$178.11	$178.10	$178.10
Purchase #2	$68.98	12.732%	$77.7625	$77.76	$77.75	$77.80
Purchase #3	$162.39	7.138%	$173.9814	$173.98	$174.00	$174.00
Purchase #4	$240.45	13.427%	$272.7352	$272.74	$272.75	$272.70
Purchase #5	$172.57	13.656%	$196.1362	$196.14	$196.15	$196.10
Purchase #6	$103.98	5.648%	$109.8528	$109.85	$109.85	$109.90
Purchase #7	$23.99	5.569%	$25.326	$25.33	$25.35	$25.30
7 purchase totals =	$933.89		$1,033.9052	$1,033.91	$1,033.95	$1,033.90