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	$51.60	11.705%	$57.6398	$57.64	$57.65	$57.60
Purchase #2	$143.46	6.357%	$152.5798	$152.58	$152.60	$152.60
Purchase #3	$231.63	13.808%	$263.6135	$263.61	$263.60	$263.60
Purchase #4	$223.87	8.517%	$242.937	$242.94	$242.95	$242.90
Purchase #5	$88.69	11.865%	$99.2131	$99.21	$99.20	$99.20
Purchase #6	$117.34	9.260%	$128.2057	$128.21	$128.20	$128.20
Purchase #7	$223.90	13.617%	$254.3885	$254.39	$254.40	$254.40
7 purchase totals =	$1,080.49		$1,198.5774	$1,198.58	$1,198.60	$1,198.50