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	$181.52	10.670%	$200.8882	$200.89	$200.90	$200.90
Purchase #2	$28.76	13.677%	$32.6935	$32.69	$32.70	$32.70
Purchase #3	$177.59	4.480%	$185.546	$185.55	$185.55	$185.50
Purchase #4	$243.25	6.620%	$259.3532	$259.35	$259.35	$259.40
Purchase #5	$131.85	11.820%	$147.4347	$147.43	$147.45	$147.40
Purchase #6	$181.40	12.490%	$204.0569	$204.06	$204.05	$204.10
Purchase #7	$108.56	11.196%	$120.7144	$120.71	$120.70	$120.70
7 purchase totals =	$1,052.93		$1,150.6869	$1,150.68	$1,150.70	$1,150.70