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	$77.37	10.758%	$85.6935	$85.69	$85.70	$85.70
Purchase #2	$221.63	6.662%	$236.395	$236.40	$236.40	$236.40
Purchase #3	$39.96	9.260%	$43.6603	$43.66	$43.65	$43.70
Purchase #4	$97.72	6.348%	$103.9233	$103.92	$103.90	$103.90
Purchase #5	$123.53	12.675%	$139.1874	$139.19	$139.20	$139.20
Purchase #6	$248.65	6.467%	$264.7302	$264.73	$264.75	$264.70
Purchase #7	$116.46	13.247%	$131.8875	$131.89	$131.90	$131.90
7 purchase totals =	$925.32		$1,005.4772	$1,005.48	$1,005.50	$1,005.50