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	$167.28	5.541%	$176.549	$176.55	$176.55	$176.50
Purchase #2	$87.40	11.588%	$97.5279	$97.53	$97.55	$97.50
Purchase #3	$75.89	5.602%	$80.1414	$80.14	$80.15	$80.10
Purchase #4	$153.42	8.590%	$166.5988	$166.60	$166.60	$166.60
Purchase #5	$52.86	12.194%	$59.3057	$59.31	$59.30	$59.30
Purchase #6	$78.42	6.242%	$83.315	$83.32	$83.30	$83.30
Purchase #7	$199.98	5.818%	$211.6148	$211.61	$211.60	$211.60
7 purchase totals =	$815.25		$875.0526	$875.06	$875.05	$874.90