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	$90.36	3.479%	$93.5036	$93.50	$93.50	$93.50
Purchase #2	$170.62	4.587%	$178.4463	$178.45	$178.45	$178.40
Purchase #3	$102.25	8.657%	$111.1018	$111.10	$111.10	$111.10
Purchase #4	$128.43	4.746%	$134.5253	$134.53	$134.55	$134.50
Purchase #5	$108.45	9.691%	$118.9599	$118.96	$118.95	$119.00
Purchase #6	$244.39	5.696%	$258.3105	$258.31	$258.30	$258.30
Purchase #7	$161.80	4.297%	$168.7525	$168.75	$168.75	$168.80
7 purchase totals =	$1,006.30		$1,063.5999	$1,063.60	$1,063.60	$1,063.60