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	$97.81	13.750%	$111.2589	$111.26	$111.25	$111.30
Purchase #2	$92.54	3.813%	$96.0686	$96.07	$96.05	$96.10
Purchase #3	$218.32	11.745%	$243.9617	$243.96	$243.95	$244.00
Purchase #4	$91.68	7.131%	$98.2177	$98.22	$98.20	$98.20
Purchase #5	$53.37	11.206%	$59.3506	$59.35	$59.35	$59.40
Purchase #6	$249.48	5.126%	$262.2683	$262.27	$262.25	$262.30
Purchase #7	$107.44	6.283%	$114.1905	$114.19	$114.20	$114.20
7 purchase totals =	$910.64		$985.3163	$985.32	$985.25	$985.50