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	$77.48	7.145%	$83.0159	$83.02	$83.00	$83.00
Purchase #2	$56.74	5.539%	$59.8828	$59.88	$59.90	$59.90
Purchase #3	$48.98	7.253%	$52.5325	$52.53	$52.55	$52.50
Purchase #4	$105.47	12.710%	$118.8752	$118.88	$118.90	$118.90
Purchase #5	$234.26	5.478%	$247.0928	$247.09	$247.10	$247.10
Purchase #6	$208.37	10.341%	$229.9175	$229.92	$229.90	$229.90
Purchase #7	$142.39	9.773%	$156.3058	$156.31	$156.30	$156.30
7 purchase totals =	$873.69		$947.6225	$947.63	$947.65	$947.60