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	$230.73	4.655%	$241.4705	$241.47	$241.45	$241.50
Purchase #2	$53.29	8.361%	$57.7456	$57.75	$57.75	$57.70
Purchase #3	$62.75	7.417%	$67.4042	$67.40	$67.40	$67.40
Purchase #4	$75.82	3.564%	$78.5222	$78.52	$78.50	$78.50
Purchase #5	$61.71	9.366%	$67.4898	$67.49	$67.50	$67.50
Purchase #6	$156.70	12.239%	$175.8785	$175.88	$175.90	$175.90
Purchase #7	$185.64	5.580%	$195.9987	$196.00	$196.00	$196.00
7 purchase totals =	$826.64		$884.5095	$884.51	$884.50	$884.50