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	$39.40	11.298%	$43.8514	$43.85	$43.85	$43.90
Purchase #2	$82.62	10.530%	$91.3199	$91.32	$91.30	$91.30
Purchase #3	$83.38	9.271%	$91.1102	$91.11	$91.10	$91.10
Purchase #4	$241.51	9.533%	$264.5331	$264.53	$264.55	$264.50
Purchase #5	$202.80	11.212%	$225.5379	$225.54	$225.55	$225.50
Purchase #6	$150.65	4.752%	$157.8089	$157.81	$157.80	$157.80
Purchase #7	$184.80	5.432%	$194.8383	$194.84	$194.85	$194.80
7 purchase totals =	$985.16		$1,068.9997	$1,069.00	$1,069.00	$1,068.90