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	$6.95	5.174%	$7.3096	$7.31	$7.30	$7.30
Purchase #2	$189.80	5.666%	$200.5541	$200.55	$200.55	$200.60
Purchase #3	$207.27	8.860%	$225.6341	$225.63	$225.65	$225.60
Purchase #4	$217.30	13.170%	$245.9184	$245.92	$245.90	$245.90
Purchase #5	$135.43	9.521%	$148.3243	$148.32	$148.30	$148.30
Purchase #6	$156.26	12.845%	$176.3316	$176.33	$176.35	$176.30
Purchase #7	$12.32	6.354%	$13.1028	$13.10	$13.10	$13.10
7 purchase totals =	$925.33		$1,017.1749	$1,017.16	$1,017.15	$1,017.10