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	$88.61	11.590%	$98.8799	$98.88	$98.90	$98.90
Purchase #2	$61.50	11.194%	$68.3843	$68.38	$68.40	$68.40
Purchase #3	$225.46	6.210%	$239.4611	$239.46	$239.45	$239.50
Purchase #4	$122.38	4.192%	$127.5102	$127.51	$127.50	$127.50
Purchase #5	$36.59	4.484%	$38.2307	$38.23	$38.25	$38.20
Purchase #6	$80.47	9.754%	$88.319	$88.32	$88.30	$88.30
Purchase #7	$187.39	5.753%	$198.1705	$198.17	$198.15	$198.20
7 purchase totals =	$802.40		$858.9557	$858.95	$858.95	$859.00