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	$72.67	7.357%	$78.0163	$78.02	$78.00	$78.00
Purchase #2	$233.25	4.235%	$243.1281	$243.13	$243.15	$243.10
Purchase #3	$168.90	3.506%	$174.8216	$174.82	$174.80	$174.80
Purchase #4	$171.64	9.153%	$187.3502	$187.35	$187.35	$187.40
Purchase #5	$144.78	7.589%	$155.7674	$155.77	$155.75	$155.80
Purchase #6	$78.99	8.349%	$85.5849	$85.58	$85.60	$85.60
Purchase #7	$238.27	4.802%	$249.7117	$249.71	$249.70	$249.70
7 purchase totals =	$1,108.50		$1,174.3802	$1,174.38	$1,174.35	$1,174.40