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	$107.56	3.251%	$111.0568	$111.06	$111.05	$111.10
Purchase #2	$228.70	5.306%	$240.8348	$240.83	$240.85	$240.80
Purchase #3	$133.53	4.422%	$139.4347	$139.43	$139.45	$139.40
Purchase #4	$219.38	4.659%	$229.6009	$229.60	$229.60	$229.60
Purchase #5	$212.74	5.202%	$223.8067	$223.81	$223.80	$223.80
Purchase #6	$53.29	8.266%	$57.695	$57.70	$57.70	$57.70
Purchase #7	$171.94	11.393%	$191.5291	$191.53	$191.55	$191.50
7 purchase totals =	$1,127.14		$1,193.9580	$1,193.96	$1,194.00	$1,193.90