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	$233.41	8.391%	$252.9954	$253.00	$253.00	$253.00
Purchase #2	$70.71	6.744%	$75.4787	$75.48	$75.50	$75.50
Purchase #3	$99.74	5.830%	$105.5548	$105.55	$105.55	$105.60
Purchase #4	$224.94	9.739%	$246.8469	$246.85	$246.85	$246.80
Purchase #5	$154.41	11.565%	$172.2675	$172.27	$172.25	$172.30
Purchase #6	$80.54	10.798%	$89.2367	$89.24	$89.25	$89.20
Purchase #7	$227.47	6.811%	$242.963	$242.96	$242.95	$243.00
7 purchase totals =	$1,091.22		$1,185.3430	$1,185.35	$1,185.35	$1,185.40