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	$188.94	3.836%	$196.1877	$196.19	$196.20	$196.20
Purchase #2	$111.90	13.636%	$127.1587	$127.16	$127.15	$127.20
Purchase #3	$42.36	3.397%	$43.799	$43.80	$43.80	$43.80
Purchase #4	$200.55	5.846%	$212.2742	$212.27	$212.25	$212.30
Purchase #5	$23.52	10.436%	$25.9745	$25.97	$25.95	$26.00
Purchase #6	$123.86	9.713%	$135.8905	$135.89	$135.90	$135.90
Purchase #7	$158.39	11.410%	$176.4623	$176.46	$176.45	$176.50
7 purchase totals =	$849.52		$917.7469	$917.74	$917.70	$917.90