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	$59.95	9.124%	$65.4198	$65.42	$65.40	$65.40
Purchase #2	$247.43	10.405%	$273.1751	$273.18	$273.20	$273.20
Purchase #3	$189.63	9.459%	$207.5671	$207.57	$207.55	$207.60
Purchase #4	$88.77	3.176%	$91.5893	$91.59	$91.60	$91.60
Purchase #5	$59.36	4.268%	$61.8935	$61.89	$61.90	$61.90
Purchase #6	$134.30	13.615%	$152.5849	$152.58	$152.60	$152.60
Purchase #7	$226.85	7.216%	$243.2195	$243.22	$243.20	$243.20
7 purchase totals =	$1,006.29		$1,095.4492	$1,095.45	$1,095.45	$1,095.50