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	$110.63	11.751%	$123.6301	$123.63	$123.65	$123.60
Purchase #2	$60.63	7.624%	$65.2524	$65.25	$65.25	$65.30
Purchase #3	$194.52	3.732%	$201.7795	$201.78	$201.80	$201.80
Purchase #4	$186.43	4.561%	$194.9331	$194.93	$194.95	$194.90
Purchase #5	$85.27	5.248%	$89.745	$89.75	$89.75	$89.70
Purchase #6	$222.46	12.396%	$250.0361	$250.04	$250.05	$250.00
Purchase #7	$100.38	4.122%	$104.5177	$104.52	$104.50	$104.50
7 purchase totals =	$960.32		$1,029.8939	$1,029.90	$1,029.95	$1,029.80