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	$176.34	13.234%	$199.6768	$199.68	$199.70	$199.70
Purchase #2	$105.35	5.553%	$111.2001	$111.20	$111.20	$111.20
Purchase #3	$208.46	7.108%	$223.2773	$223.28	$223.30	$223.30
Purchase #4	$246.34	6.111%	$261.3938	$261.39	$261.40	$261.40
Purchase #5	$186.91	5.375%	$196.9564	$196.96	$196.95	$197.00
Purchase #6	$67.66	6.821%	$72.2751	$72.28	$72.30	$72.30
Purchase #7	$175.75	6.811%	$187.7203	$187.72	$187.70	$187.70
7 purchase totals =	$1,166.81		$1,252.4998	$1,252.51	$1,252.55	$1,252.60