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	$193.77	6.614%	$206.5859	$206.59	$206.60	$206.60
Purchase #2	$169.50	11.666%	$189.2739	$189.27	$189.25	$189.30
Purchase #3	$49.91	11.405%	$55.6022	$55.60	$55.60	$55.60
Purchase #4	$164.78	13.860%	$187.6185	$187.62	$187.60	$187.60
Purchase #5	$123.46	13.204%	$139.7617	$139.76	$139.75	$139.80
Purchase #6	$207.72	7.298%	$222.8794	$222.88	$222.90	$222.90
Purchase #7	$96.87	11.657%	$108.1621	$108.16	$108.15	$108.20
7 purchase totals =	$1,006.01		$1,109.8837	$1,109.88	$1,109.85	$1,110.00