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	$161.57	6.172%	$171.5421	$171.54	$171.55	$171.50
Purchase #2	$185.87	7.667%	$200.1207	$200.12	$200.10	$200.10
Purchase #3	$110.38	5.578%	$116.537	$116.54	$116.55	$116.50
Purchase #4	$79.94	12.761%	$90.1411	$90.14	$90.15	$90.10
Purchase #5	$55.96	13.270%	$63.3859	$63.39	$63.40	$63.40
Purchase #6	$155.53	13.326%	$176.2559	$176.26	$176.25	$176.30
Purchase #7	$137.33	3.451%	$142.0693	$142.07	$142.05	$142.10
7 purchase totals =	$886.58		$960.0520	$960.06	$960.05	$960.00