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	$91.64	4.208%	$95.4962	$95.50	$95.50	$95.50
Purchase #2	$175.32	7.137%	$187.8326	$187.83	$187.85	$187.80
Purchase #3	$117.34	8.583%	$127.4113	$127.41	$127.40	$127.40
Purchase #4	$128.64	4.517%	$134.4507	$134.45	$134.45	$134.50
Purchase #5	$178.33	4.555%	$186.4529	$186.45	$186.45	$186.50
Purchase #6	$45.69	12.600%	$51.4469	$51.45	$51.45	$51.40
Purchase #7	$194.67	5.372%	$205.1277	$205.13	$205.15	$205.10
7 purchase totals =	$931.63		$988.2183	$988.22	$988.25	$988.20