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	$209.30	6.690%	$223.3022	$223.30	$223.30	$223.30
Purchase #2	$136.73	9.663%	$149.9422	$149.94	$149.95	$149.90
Purchase #3	$9.63	7.102%	$10.3139	$10.31	$10.30	$10.30
Purchase #4	$214.47	4.241%	$223.5657	$223.57	$223.55	$223.60
Purchase #5	$145.64	6.720%	$155.427	$155.43	$155.45	$155.40
Purchase #6	$55.48	3.433%	$57.3846	$57.38	$57.40	$57.40
Purchase #7	$219.40	10.194%	$241.7656	$241.77	$241.75	$241.80
7 purchase totals =	$990.65		$1,061.7012	$1,061.70	$1,061.70	$1,061.70