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	$128.37	11.459%	$143.0799	$143.08	$143.10	$143.10
Purchase #2	$65.80	8.686%	$71.5154	$71.52	$71.50	$71.50
Purchase #3	$238.33	8.255%	$258.0041	$258.00	$258.00	$258.00
Purchase #4	$88.76	3.609%	$91.9633	$91.96	$91.95	$92.00
Purchase #5	$223.83	7.863%	$241.4298	$241.43	$241.45	$241.40
Purchase #6	$72.56	11.646%	$81.0103	$81.01	$81.00	$81.00
Purchase #7	$233.43	9.515%	$255.6409	$255.64	$255.65	$255.60
7 purchase totals =	$1,051.08		$1,142.6437	$1,142.64	$1,142.65	$1,142.60