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	$118.72	7.315%	$127.4044	$127.40	$127.40	$127.40
Purchase #2	$71.44	13.339%	$80.9694	$80.97	$80.95	$81.00
Purchase #3	$111.79	13.839%	$127.2606	$127.26	$127.25	$127.30
Purchase #4	$135.28	6.646%	$144.2707	$144.27	$144.25	$144.30
Purchase #5	$222.91	13.159%	$252.2427	$252.24	$252.25	$252.20
Purchase #6	$57.94	13.846%	$65.9624	$65.96	$65.95	$66.00
Purchase #7	$81.87	9.821%	$89.9105	$89.91	$89.90	$89.90
7 purchase totals =	$799.95		$888.0207	$888.01	$887.95	$888.10