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	$211.64	3.734%	$219.5426	$219.54	$219.55	$219.50
Purchase #2	$221.69	7.679%	$238.7136	$238.71	$238.70	$238.70
Purchase #3	$36.30	12.436%	$40.8143	$40.81	$40.80	$40.80
Purchase #4	$224.92	11.377%	$250.5091	$250.51	$250.50	$250.50
Purchase #5	$21.88	4.704%	$22.9092	$22.91	$22.90	$22.90
Purchase #6	$23.82	3.395%	$24.6287	$24.63	$24.65	$24.60
Purchase #7	$189.82	8.321%	$205.6149	$205.61	$205.60	$205.60
7 purchase totals =	$930.07		$1,002.7324	$1,002.72	$1,002.70	$1,002.60