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	$192.59	3.218%	$198.7875	$198.79	$198.80	$198.80
Purchase #2	$224.88	9.531%	$246.3133	$246.31	$246.30	$246.30
Purchase #3	$123.76	10.648%	$136.938	$136.94	$136.95	$136.90
Purchase #4	$97.27	3.551%	$100.7241	$100.72	$100.70	$100.70
Purchase #5	$177.73	4.232%	$185.2515	$185.25	$185.25	$185.30
Purchase #6	$237.57	13.811%	$270.3808	$270.38	$270.40	$270.40
Purchase #7	$168.49	6.494%	$179.4317	$179.43	$179.45	$179.40
7 purchase totals =	$1,222.29		$1,317.8269	$1,317.82	$1,317.85	$1,317.80