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	$194.32	12.293%	$218.2078	$218.21	$218.20	$218.20
Purchase #2	$241.28	11.272%	$268.4771	$268.48	$268.50	$268.50
Purchase #3	$183.46	12.725%	$206.8053	$206.81	$206.80	$206.80
Purchase #4	$42.75	4.425%	$44.6417	$44.64	$44.65	$44.60
Purchase #5	$53.35	7.781%	$57.5012	$57.50	$57.50	$57.50
Purchase #6	$56.51	5.511%	$59.6243	$59.62	$59.60	$59.60
Purchase #7	$207.58	10.605%	$229.5939	$229.59	$229.60	$229.60
7 purchase totals =	$979.25		$1,084.8513	$1,084.85	$1,084.85	$1,084.80