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	$64.98	13.314%	$73.6314	$73.63	$73.65	$73.60
Purchase #2	$104.39	3.728%	$108.2817	$108.28	$108.30	$108.30
Purchase #3	$239.78	10.600%	$265.1967	$265.20	$265.20	$265.20
Purchase #4	$41.61	3.846%	$43.2103	$43.21	$43.20	$43.20
Purchase #5	$179.59	3.554%	$185.9726	$185.97	$185.95	$186.00
Purchase #6	$52.28	13.367%	$59.2683	$59.27	$59.25	$59.30
Purchase #7	$45.53	7.434%	$48.9147	$48.91	$48.90	$48.90
7 purchase totals =	$728.16		$784.4757	$784.47	$784.45	$784.50