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	$146.37	12.205%	$164.2345	$164.23	$164.25	$164.20
Purchase #2	$54.59	6.805%	$58.3048	$58.30	$58.30	$58.30
Purchase #3	$111.80	5.821%	$118.3079	$118.31	$118.30	$118.30
Purchase #4	$183.57	3.219%	$189.4791	$189.48	$189.50	$189.50
Purchase #5	$184.72	6.304%	$196.3647	$196.36	$196.35	$196.40
Purchase #6	$84.93	11.193%	$94.4362	$94.44	$94.45	$94.40
Purchase #7	$204.79	6.867%	$218.8529	$218.85	$218.85	$218.90
7 purchase totals =	$970.77		$1,039.9801	$1,039.97	$1,040.00	$1,040.00