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	$61.57	7.463%	$66.165	$66.17	$66.15	$66.20
Purchase #2	$79.94	8.287%	$86.5646	$86.56	$86.55	$86.60
Purchase #3	$138.97	3.202%	$143.4198	$143.42	$143.40	$143.40
Purchase #4	$98.73	13.575%	$112.1326	$112.13	$112.15	$112.10
Purchase #5	$218.75	11.678%	$244.2956	$244.30	$244.30	$244.30
Purchase #6	$226.37	5.514%	$238.852	$238.85	$238.85	$238.90
Purchase #7	$161.81	3.145%	$166.8989	$166.90	$166.90	$166.90
7 purchase totals =	$986.14		$1,058.3285	$1,058.33	$1,058.30	$1,058.40