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	$186.32	5.385%	$196.3533	$196.35	$196.35	$196.40
Purchase #2	$46.99	4.150%	$48.9401	$48.94	$48.95	$48.90
Purchase #3	$227.89	11.486%	$254.0654	$254.07	$254.05	$254.10
Purchase #4	$97.50	3.526%	$100.9379	$100.94	$100.95	$100.90
Purchase #5	$91.40	5.314%	$96.257	$96.26	$96.25	$96.30
Purchase #6	$123.85	8.354%	$134.1964	$134.20	$134.20	$134.20
Purchase #7	$164.65	6.263%	$174.962	$174.96	$174.95	$175.00
7 purchase totals =	$938.60		$1,005.7121	$1,005.72	$1,005.70	$1,005.80