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	$219.95	9.144%	$240.0622	$240.06	$240.05	$240.10
Purchase #2	$152.60	10.830%	$169.1266	$169.13	$169.15	$169.10
Purchase #3	$140.70	4.425%	$146.926	$146.93	$146.95	$146.90
Purchase #4	$101.44	6.229%	$107.7587	$107.76	$107.75	$107.80
Purchase #5	$137.94	5.341%	$145.3074	$145.31	$145.30	$145.30
Purchase #6	$68.99	5.495%	$72.781	$72.78	$72.80	$72.80
Purchase #7	$81.68	11.262%	$90.8788	$90.88	$90.90	$90.90
7 purchase totals =	$903.30		$972.8407	$972.85	$972.90	$972.90