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	$130.34	11.163%	$144.8899	$144.89	$144.90	$144.90
Purchase #2	$115.62	6.708%	$123.3758	$123.38	$123.40	$123.40
Purchase #3	$242.52	13.541%	$275.3596	$275.36	$275.35	$275.40
Purchase #4	$31.90	4.442%	$33.317	$33.32	$33.30	$33.30
Purchase #5	$123.86	3.150%	$127.7616	$127.76	$127.75	$127.80
Purchase #6	$223.55	5.835%	$236.5941	$236.59	$236.60	$236.60
Purchase #7	$106.34	9.657%	$116.6093	$116.61	$116.60	$116.60
7 purchase totals =	$974.13		$1,057.9073	$1,057.91	$1,057.90	$1,058.00