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	$199.38	6.466%	$212.2719	$212.27	$212.25	$212.30
Purchase #2	$66.34	7.839%	$71.5404	$71.54	$71.55	$71.50
Purchase #3	$86.33	5.337%	$90.9374	$90.94	$90.95	$90.90
Purchase #4	$214.83	9.216%	$234.6287	$234.63	$234.65	$234.60
Purchase #5	$205.94	8.508%	$223.4614	$223.46	$223.45	$223.50
Purchase #6	$229.54	8.201%	$248.3646	$248.36	$248.35	$248.40
Purchase #7	$131.34	10.301%	$144.8693	$144.87	$144.85	$144.90
7 purchase totals =	$1,133.70		$1,226.0737	$1,226.07	$1,226.05	$1,226.10