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	$55.67	5.328%	$58.6361	$58.64	$58.65	$58.60
Purchase #2	$76.43	12.159%	$85.7231	$85.72	$85.70	$85.70
Purchase #3	$218.40	7.180%	$234.0811	$234.08	$234.10	$234.10
Purchase #4	$206.54	7.671%	$222.3837	$222.38	$222.40	$222.40
Purchase #5	$101.77	11.335%	$113.3056	$113.31	$113.30	$113.30
Purchase #6	$210.40	6.250%	$223.55	$223.55	$223.55	$223.60
Purchase #7	$166.32	11.803%	$185.9507	$185.95	$185.95	$186.00
7 purchase totals =	$1,035.53		$1,123.6303	$1,123.63	$1,123.65	$1,123.70