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	$76.77	7.412%	$82.4602	$82.46	$82.45	$82.50
Purchase #2	$53.28	10.809%	$59.039	$59.04	$59.05	$59.00
Purchase #3	$227.35	4.374%	$237.2943	$237.29	$237.30	$237.30
Purchase #4	$241.46	8.873%	$262.8847	$262.88	$262.90	$262.90
Purchase #5	$181.28	4.247%	$188.979	$188.98	$189.00	$189.00
Purchase #6	$60.40	9.151%	$65.9272	$65.93	$65.95	$65.90
Purchase #7	$239.82	4.452%	$250.4968	$250.50	$250.50	$250.50
7 purchase totals =	$1,080.36		$1,147.0812	$1,147.08	$1,147.15	$1,147.10