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	$236.74	9.171%	$258.4514	$258.45	$258.45	$258.50
Purchase #2	$127.41	6.163%	$135.2623	$135.26	$135.25	$135.30
Purchase #3	$39.39	3.850%	$40.9065	$40.91	$40.90	$40.90
Purchase #4	$43.88	6.441%	$46.7063	$46.71	$46.70	$46.70
Purchase #5	$105.42	5.635%	$111.3604	$111.36	$111.35	$111.40
Purchase #6	$236.94	3.779%	$245.894	$245.89	$245.90	$245.90
Purchase #7	$64.39	10.426%	$71.1033	$71.10	$71.10	$71.10
7 purchase totals =	$854.17		$909.6842	$909.68	$909.65	$909.80