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	$179.69	13.193%	$203.3965	$203.40	$203.40	$203.40
Purchase #2	$175.47	11.821%	$196.2123	$196.21	$196.20	$196.20
Purchase #3	$101.86	3.198%	$105.1175	$105.12	$105.10	$105.10
Purchase #4	$222.89	3.594%	$230.9007	$230.90	$230.90	$230.90
Purchase #5	$94.37	4.186%	$98.3203	$98.32	$98.30	$98.30
Purchase #6	$166.55	11.615%	$185.8948	$185.89	$185.90	$185.90
Purchase #7	$236.62	3.783%	$245.5713	$245.57	$245.55	$245.60
7 purchase totals =	$1,177.45		$1,265.4134	$1,265.41	$1,265.35	$1,265.40