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	$114.76	11.684%	$128.1686	$128.17	$128.15	$128.20
Purchase #2	$120.45	5.632%	$127.2337	$127.23	$127.25	$127.20
Purchase #3	$6.86	13.107%	$7.7591	$7.76	$7.75	$7.80
Purchase #4	$33.85	12.695%	$38.1473	$38.15	$38.15	$38.10
Purchase #5	$244.60	11.200%	$271.9952	$272.00	$272.00	$272.00
Purchase #6	$152.45	7.850%	$164.4173	$164.42	$164.40	$164.40
Purchase #7	$110.31	6.184%	$117.1316	$117.13	$117.15	$117.10
7 purchase totals =	$783.28		$854.8528	$854.86	$854.85	$854.80