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	$191.89	13.724%	$218.225	$218.23	$218.25	$218.20
Purchase #2	$176.77	6.123%	$187.5936	$187.59	$187.60	$187.60
Purchase #3	$165.95	13.537%	$188.4147	$188.41	$188.40	$188.40
Purchase #4	$200.70	11.793%	$224.3686	$224.37	$224.35	$224.40
Purchase #5	$98.33	3.251%	$101.5267	$101.53	$101.55	$101.50
Purchase #6	$95.73	4.481%	$100.0197	$100.02	$100.00	$100.00
Purchase #7	$86.31	8.414%	$93.5721	$93.57	$93.55	$93.60
7 purchase totals =	$1,015.68		$1,113.7204	$1,113.72	$1,113.70	$1,113.70