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	$211.82	13.332%	$240.0598	$240.06	$240.05	$240.10
Purchase #2	$17.86	4.813%	$18.7196	$18.72	$18.70	$18.70
Purchase #3	$55.59	11.741%	$62.1168	$62.12	$62.10	$62.10
Purchase #4	$158.65	3.711%	$164.5375	$164.54	$164.55	$164.50
Purchase #5	$51.31	5.113%	$53.9335	$53.93	$53.95	$53.90
Purchase #6	$119.29	6.647%	$127.2192	$127.22	$127.20	$127.20
Purchase #7	$55.26	3.849%	$57.387	$57.39	$57.40	$57.40
7 purchase totals =	$669.78		$723.9734	$723.98	$723.95	$723.90