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	$96.85	11.851%	$108.3277	$108.33	$108.35	$108.30
Purchase #2	$186.93	5.199%	$196.6485	$196.65	$196.65	$196.60
Purchase #3	$189.51	5.575%	$200.0752	$200.08	$200.10	$200.10
Purchase #4	$22.36	9.370%	$24.4551	$24.46	$24.45	$24.50
Purchase #5	$89.95	12.470%	$101.1668	$101.17	$101.15	$101.20
Purchase #6	$136.72	4.593%	$142.9995	$143.00	$143.00	$143.00
Purchase #7	$81.32	5.377%	$85.6926	$85.69	$85.70	$85.70
7 purchase totals =	$803.64		$859.3654	$859.38	$859.40	$859.40