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	$187.86	12.109%	$210.608	$210.61	$210.60	$210.60
Purchase #2	$213.57	4.234%	$222.6126	$222.61	$222.60	$222.60
Purchase #3	$51.58	4.505%	$53.9037	$53.90	$53.90	$53.90
Purchase #4	$16.74	8.656%	$18.189	$18.19	$18.20	$18.20
Purchase #5	$140.48	7.229%	$150.6353	$150.64	$150.65	$150.60
Purchase #6	$189.44	5.494%	$199.8478	$199.85	$199.85	$199.80
Purchase #7	$160.71	13.610%	$182.5826	$182.58	$182.60	$182.60
7 purchase totals =	$960.38		$1,038.3790	$1,038.38	$1,038.40	$1,038.30