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	$247.59	6.754%	$264.3122	$264.31	$264.30	$264.30
Purchase #2	$27.81	3.846%	$28.8796	$28.88	$28.90	$28.90
Purchase #3	$186.33	5.405%	$196.4011	$196.40	$196.40	$196.40
Purchase #4	$154.35	12.290%	$173.3196	$173.32	$173.30	$173.30
Purchase #5	$150.68	3.150%	$155.4264	$155.43	$155.45	$155.40
Purchase #6	$197.33	4.733%	$206.6696	$206.67	$206.65	$206.70
Purchase #7	$146.47	8.134%	$158.3839	$158.38	$158.40	$158.40
7 purchase totals =	$1,110.56		$1,183.3924	$1,183.39	$1,183.40	$1,183.40