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	$103.35	3.838%	$107.3166	$107.32	$107.30	$107.30
Purchase #2	$82.32	4.559%	$86.073	$86.07	$86.05	$86.10
Purchase #3	$89.93	9.354%	$98.3421	$98.34	$98.35	$98.30
Purchase #4	$248.63	6.454%	$264.6766	$264.68	$264.70	$264.70
Purchase #5	$136.67	11.536%	$152.4363	$152.44	$152.45	$152.40
Purchase #6	$131.63	10.443%	$145.3761	$145.38	$145.40	$145.40
Purchase #7	$236.32	8.873%	$257.2887	$257.29	$257.30	$257.30
7 purchase totals =	$1,028.85		$1,111.5094	$1,111.52	$1,111.55	$1,111.50