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	$230.42	5.413%	$242.8926	$242.89	$242.90	$242.90
Purchase #2	$84.44	5.579%	$89.1509	$89.15	$89.15	$89.20
Purchase #3	$91.72	13.741%	$104.3232	$104.32	$104.30	$104.30
Purchase #4	$227.90	9.302%	$249.0993	$249.10	$249.10	$249.10
Purchase #5	$141.27	9.190%	$154.2527	$154.25	$154.25	$154.30
Purchase #6	$147.27	11.576%	$164.318	$164.32	$164.30	$164.30
Purchase #7	$114.69	10.376%	$126.5902	$126.59	$126.60	$126.60
7 purchase totals =	$1,037.71		$1,130.6269	$1,130.62	$1,130.60	$1,130.70