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	$122.28	10.448%	$135.0558	$135.06	$135.05	$135.10
Purchase #2	$173.70	9.645%	$190.4534	$190.45	$190.45	$190.50
Purchase #3	$77.35	4.724%	$81.004	$81.00	$81.00	$81.00
Purchase #4	$166.61	3.687%	$172.7529	$172.75	$172.75	$172.80
Purchase #5	$173.69	10.326%	$191.6252	$191.63	$191.65	$191.60
Purchase #6	$79.95	11.558%	$89.1906	$89.19	$89.20	$89.20
Purchase #7	$151.69	8.164%	$164.074	$164.07	$164.05	$164.10
7 purchase totals =	$945.27		$1,024.1559	$1,024.15	$1,024.15	$1,024.30