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	$245.50	9.392%	$268.5574	$268.56	$268.55	$268.60
Purchase #2	$244.65	3.577%	$253.4011	$253.40	$253.40	$253.40
Purchase #3	$141.71	10.455%	$156.5258	$156.53	$156.55	$156.50
Purchase #4	$247.74	11.367%	$275.9006	$275.90	$275.90	$275.90
Purchase #5	$183.93	3.332%	$190.0585	$190.06	$190.05	$190.10
Purchase #6	$78.85	5.128%	$82.8934	$82.89	$82.90	$82.90
Purchase #7	$206.96	10.536%	$228.7653	$228.77	$228.75	$228.80
7 purchase totals =	$1,349.34		$1,456.1021	$1,456.11	$1,456.10	$1,456.20