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	$82.50	4.857%	$86.507	$86.51	$86.50	$86.50
Purchase #2	$131.88	3.224%	$136.1318	$136.13	$136.15	$136.10
Purchase #3	$6.79	13.854%	$7.7307	$7.73	$7.75	$7.70
Purchase #4	$25.70	12.315%	$28.865	$28.87	$28.85	$28.90
Purchase #5	$115.70	10.133%	$127.4239	$127.42	$127.40	$127.40
Purchase #6	$140.40	13.665%	$159.5857	$159.59	$159.60	$159.60
Purchase #7	$75.79	4.571%	$79.2544	$79.25	$79.25	$79.30
7 purchase totals =	$578.76		$625.4985	$625.50	$625.50	$625.50