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	$33.35	6.677%	$35.5768	$35.58	$35.60	$35.60
Purchase #2	$96.81	8.509%	$105.0476	$105.05	$105.05	$105.00
Purchase #3	$54.70	8.470%	$59.3331	$59.33	$59.35	$59.30
Purchase #4	$147.64	4.227%	$153.8807	$153.88	$153.90	$153.90
Purchase #5	$131.47	3.452%	$136.0083	$136.01	$136.00	$136.00
Purchase #6	$191.59	6.197%	$203.4628	$203.46	$203.45	$203.50
Purchase #7	$220.92	12.705%	$248.9879	$248.99	$249.00	$249.00
7 purchase totals =	$876.48		$942.2972	$942.30	$942.35	$942.30