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	$211.50	10.297%	$233.2782	$233.28	$233.30	$233.30
Purchase #2	$52.44	4.686%	$54.8973	$54.90	$54.90	$54.90
Purchase #3	$14.46	9.117%	$15.7783	$15.78	$15.80	$15.80
Purchase #4	$88.27	10.752%	$97.7608	$97.76	$97.75	$97.80
Purchase #5	$62.36	12.717%	$70.2903	$70.29	$70.30	$70.30
Purchase #6	$79.44	13.856%	$90.4472	$90.45	$90.45	$90.40
Purchase #7	$41.85	10.117%	$46.084	$46.08	$46.10	$46.10
7 purchase totals =	$550.32		$608.5361	$608.54	$608.60	$608.60