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	$239.76	4.192%	$249.8107	$249.81	$249.80	$249.80
Purchase #2	$218.82	6.717%	$233.5181	$233.52	$233.50	$233.50
Purchase #3	$234.36	3.109%	$241.6463	$241.65	$241.65	$241.60
Purchase #4	$57.56	12.312%	$64.6468	$64.65	$64.65	$64.60
Purchase #5	$35.76	13.526%	$40.5969	$40.60	$40.60	$40.60
Purchase #6	$160.52	4.338%	$167.4834	$167.48	$167.50	$167.50
Purchase #7	$33.66	11.154%	$37.4144	$37.41	$37.40	$37.40
7 purchase totals =	$980.44		$1,035.1166	$1,035.12	$1,035.10	$1,035.00