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	$131.33	5.776%	$138.9156	$138.92	$138.90	$138.90
Purchase #2	$106.63	6.872%	$113.9576	$113.96	$113.95	$114.00
Purchase #3	$142.57	7.170%	$152.7923	$152.79	$152.80	$152.80
Purchase #4	$220.74	8.230%	$238.9069	$238.91	$238.90	$238.90
Purchase #5	$154.99	12.649%	$174.5947	$174.59	$174.60	$174.60
Purchase #6	$80.67	12.462%	$90.7231	$90.72	$90.70	$90.70
Purchase #7	$119.65	3.489%	$123.8246	$123.82	$123.80	$123.80
7 purchase totals =	$956.58		$1,033.7148	$1,033.71	$1,033.65	$1,033.70