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	$81.54	12.309%	$91.5768	$91.58	$91.60	$91.60
Purchase #2	$126.36	6.457%	$134.5191	$134.52	$134.50	$134.50
Purchase #3	$202.28	4.744%	$211.8762	$211.88	$211.90	$211.90
Purchase #4	$97.70	12.360%	$109.7757	$109.78	$109.80	$109.80
Purchase #5	$219.29	9.410%	$239.9252	$239.93	$239.95	$239.90
Purchase #6	$59.94	9.642%	$65.7194	$65.72	$65.70	$65.70
Purchase #7	$182.78	13.606%	$207.649	$207.65	$207.65	$207.60
7 purchase totals =	$969.89		$1,061.0414	$1,061.06	$1,061.10	$1,061.00