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	$78.51	13.794%	$89.3397	$89.34	$89.35	$89.30
Purchase #2	$144.60	5.359%	$152.3491	$152.35	$152.35	$152.30
Purchase #3	$73.58	5.810%	$77.855	$77.86	$77.85	$77.90
Purchase #4	$170.94	5.718%	$180.7143	$180.71	$180.70	$180.70
Purchase #5	$125.92	9.191%	$137.4933	$137.49	$137.50	$137.50
Purchase #6	$95.41	7.486%	$102.5524	$102.55	$102.55	$102.60
Purchase #7	$244.59	6.609%	$260.755	$260.76	$260.75	$260.80
7 purchase totals =	$933.55		$1,001.0588	$1,001.06	$1,001.05	$1,001.10