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	$218.47	3.318%	$225.7188	$225.72	$225.70	$225.70
Purchase #2	$225.83	6.523%	$240.5609	$240.56	$240.55	$240.60
Purchase #3	$36.60	7.121%	$39.2063	$39.21	$39.20	$39.20
Purchase #4	$128.72	12.113%	$144.3119	$144.31	$144.30	$144.30
Purchase #5	$162.89	12.782%	$183.7106	$183.71	$183.70	$183.70
Purchase #6	$144.73	13.845%	$164.7679	$164.77	$164.75	$164.80
Purchase #7	$118.65	7.260%	$127.264	$127.26	$127.25	$127.30
7 purchase totals =	$1,035.89		$1,125.5404	$1,125.54	$1,125.45	$1,125.60