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	$109.47	4.546%	$114.4465	$114.45	$114.45	$114.40
Purchase #2	$55.44	13.106%	$62.706	$62.71	$62.70	$62.70
Purchase #3	$175.96	9.407%	$192.5126	$192.51	$192.50	$192.50
Purchase #4	$70.36	4.379%	$73.4411	$73.44	$73.45	$73.40
Purchase #5	$173.88	9.461%	$190.3308	$190.33	$190.35	$190.30
Purchase #6	$82.88	7.683%	$89.2477	$89.25	$89.25	$89.20
Purchase #7	$56.73	9.636%	$62.1965	$62.20	$62.20	$62.20
7 purchase totals =	$724.72		$784.8812	$784.89	$784.90	$784.70