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	$82.25	4.266%	$85.7588	$85.76	$85.75	$85.80
Purchase #2	$6.99	7.591%	$7.5206	$7.52	$7.50	$7.50
Purchase #3	$79.76	3.159%	$82.2796	$82.28	$82.30	$82.30
Purchase #4	$208.83	7.450%	$224.3878	$224.39	$224.40	$224.40
Purchase #5	$54.52	9.762%	$59.8422	$59.84	$59.85	$59.80
Purchase #6	$161.62	3.247%	$166.8678	$166.87	$166.85	$166.90
Purchase #7	$109.88	11.586%	$122.6107	$122.61	$122.60	$122.60
7 purchase totals =	$703.85		$749.2675	$749.27	$749.25	$749.30