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	$210.66	12.660%	$237.3296	$237.33	$237.35	$237.30
Purchase #2	$86.96	4.507%	$90.8793	$90.88	$90.90	$90.90
Purchase #3	$181.38	10.538%	$200.4938	$200.49	$200.50	$200.50
Purchase #4	$222.43	6.860%	$237.6887	$237.69	$237.70	$237.70
Purchase #5	$206.68	7.420%	$222.0157	$222.02	$222.00	$222.00
Purchase #6	$237.40	3.113%	$244.7903	$244.79	$244.80	$244.80
Purchase #7	$95.36	4.506%	$99.6569	$99.66	$99.65	$99.70
7 purchase totals =	$1,240.87		$1,332.8543	$1,332.86	$1,332.90	$1,332.90