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	$102.90	6.853%	$109.9517	$109.95	$109.95	$110.00
Purchase #2	$127.47	10.199%	$140.4707	$140.47	$140.45	$140.50
Purchase #3	$182.59	7.443%	$196.1802	$196.18	$196.20	$196.20
Purchase #4	$17.80	8.455%	$19.305	$19.31	$19.30	$19.30
Purchase #5	$114.76	9.713%	$125.9066	$125.91	$125.90	$125.90
Purchase #6	$160.93	4.591%	$168.3183	$168.32	$168.30	$168.30
Purchase #7	$39.70	4.852%	$41.6262	$41.63	$41.65	$41.60
7 purchase totals =	$746.15		$801.7587	$801.77	$801.75	$801.80