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	$247.81	5.796%	$262.1731	$262.17	$262.15	$262.20
Purchase #2	$144.84	13.547%	$164.4615	$164.46	$164.45	$164.50
Purchase #3	$105.92	3.104%	$109.2078	$109.21	$109.20	$109.20
Purchase #4	$206.82	9.349%	$226.1556	$226.16	$226.15	$226.20
Purchase #5	$69.41	10.288%	$76.5509	$76.55	$76.55	$76.60
Purchase #6	$78.88	13.164%	$89.2638	$89.26	$89.25	$89.30
Purchase #7	$238.57	12.455%	$268.2839	$268.28	$268.30	$268.30
7 purchase totals =	$1,092.25		$1,196.0966	$1,196.09	$1,196.05	$1,196.30