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	$233.90	5.480%	$246.7177	$246.72	$246.70	$246.70
Purchase #2	$95.68	4.238%	$99.7349	$99.73	$99.75	$99.70
Purchase #3	$149.29	3.411%	$154.3823	$154.38	$154.40	$154.40
Purchase #4	$110.69	3.398%	$114.4512	$114.45	$114.45	$114.50
Purchase #5	$178.31	5.693%	$188.4612	$188.46	$188.45	$188.50
Purchase #6	$62.75	7.756%	$67.6169	$67.62	$67.60	$67.60
Purchase #7	$237.48	9.557%	$260.176	$260.18	$260.20	$260.20
7 purchase totals =	$1,068.10		$1,131.5402	$1,131.54	$1,131.55	$1,131.60