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	$207.56	3.404%	$214.6253	$214.63	$214.65	$214.60
Purchase #2	$158.81	12.570%	$178.7724	$178.77	$178.75	$178.80
Purchase #3	$234.72	6.706%	$250.4603	$250.46	$250.45	$250.50
Purchase #4	$50.33	10.482%	$55.6056	$55.61	$55.60	$55.60
Purchase #5	$26.77	3.137%	$27.6098	$27.61	$27.60	$27.60
Purchase #6	$87.38	10.489%	$96.5453	$96.55	$96.55	$96.50
Purchase #7	$200.94	7.564%	$216.1391	$216.14	$216.15	$216.10
7 purchase totals =	$966.51		$1,039.7578	$1,039.77	$1,039.75	$1,039.70