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	$55.44	13.367%	$62.8507	$62.85	$62.85	$62.90
Purchase #2	$187.69	9.535%	$205.5862	$205.59	$205.60	$205.60
Purchase #3	$161.53	13.655%	$183.5869	$183.59	$183.60	$183.60
Purchase #4	$32.46	12.223%	$36.4276	$36.43	$36.45	$36.40
Purchase #5	$68.81	5.399%	$72.5251	$72.53	$72.55	$72.50
Purchase #6	$243.42	10.216%	$268.2878	$268.29	$268.30	$268.30
Purchase #7	$169.72	10.746%	$187.9581	$187.96	$187.95	$188.00
7 purchase totals =	$919.07		$1,017.2224	$1,017.24	$1,017.30	$1,017.30