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	$176.92	7.363%	$189.9466	$189.95	$189.95	$189.90
Purchase #2	$127.86	7.453%	$137.3894	$137.39	$137.40	$137.40
Purchase #3	$197.89	12.213%	$222.0583	$222.06	$222.05	$222.10
Purchase #4	$238.39	10.544%	$263.5258	$263.53	$263.55	$263.50
Purchase #5	$84.59	6.385%	$89.9911	$89.99	$90.00	$90.00
Purchase #6	$153.89	3.638%	$159.4885	$159.49	$159.50	$159.50
Purchase #7	$131.96	5.170%	$138.7823	$138.78	$138.80	$138.80
7 purchase totals =	$1,111.50		$1,201.1820	$1,201.19	$1,201.25	$1,201.20