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	$148.54	6.379%	$158.0154	$158.02	$158.00	$158.00
Purchase #2	$89.99	13.370%	$102.0217	$102.02	$102.00	$102.00
Purchase #3	$212.84	13.102%	$240.7263	$240.73	$240.75	$240.70
Purchase #4	$204.94	3.421%	$211.951	$211.95	$211.95	$212.00
Purchase #5	$142.42	3.407%	$147.2722	$147.27	$147.25	$147.30
Purchase #6	$124.29	12.228%	$139.4882	$139.49	$139.50	$139.50
Purchase #7	$16.37	6.214%	$17.3872	$17.39	$17.40	$17.40
7 purchase totals =	$939.39		$1,016.8620	$1,016.87	$1,016.85	$1,016.90