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	$152.86	5.412%	$161.1328	$161.13	$161.15	$161.10
Purchase #2	$141.54	5.204%	$148.9057	$148.91	$148.90	$148.90
Purchase #3	$185.80	3.367%	$192.0559	$192.06	$192.05	$192.10
Purchase #4	$199.75	13.836%	$227.3874	$227.39	$227.40	$227.40
Purchase #5	$120.71	6.807%	$128.9267	$128.93	$128.95	$128.90
Purchase #6	$139.89	12.142%	$156.8754	$156.88	$156.90	$156.90
Purchase #7	$39.60	4.294%	$41.3004	$41.30	$41.30	$41.30
7 purchase totals =	$980.15		$1,056.5843	$1,056.60	$1,056.65	$1,056.60