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	$55.36	6.474%	$58.944	$58.94	$58.95	$58.90
Purchase #2	$47.71	9.419%	$52.2038	$52.20	$52.20	$52.20
Purchase #3	$73.83	6.590%	$78.6954	$78.70	$78.70	$78.70
Purchase #4	$112.95	12.847%	$127.4607	$127.46	$127.45	$127.50
Purchase #5	$31.80	4.544%	$33.245	$33.25	$33.25	$33.20
Purchase #6	$193.33	4.768%	$202.548	$202.55	$202.55	$202.50
Purchase #7	$42.88	6.222%	$45.548	$45.55	$45.55	$45.50
7 purchase totals =	$557.86		$598.6449	$598.65	$598.65	$598.50