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	$176.92	10.254%	$195.0614	$195.06	$195.05	$195.10
Purchase #2	$90.64	8.609%	$98.4432	$98.44	$98.45	$98.40
Purchase #3	$68.90	5.874%	$72.9472	$72.95	$72.95	$72.90
Purchase #4	$250.65	5.478%	$264.3806	$264.38	$264.40	$264.40
Purchase #5	$147.87	6.599%	$157.6279	$157.63	$157.65	$157.60
Purchase #6	$79.97	13.622%	$90.8635	$90.86	$90.85	$90.90
Purchase #7	$33.31	9.586%	$36.5031	$36.50	$36.50	$36.50
7 purchase totals =	$848.26		$915.8269	$915.82	$915.85	$915.80