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	$152.43	6.554%	$162.4203	$162.42	$162.40	$162.40
Purchase #2	$228.52	6.576%	$243.5475	$243.55	$243.55	$243.50
Purchase #3	$41.38	13.359%	$46.908	$46.91	$46.90	$46.90
Purchase #4	$53.90	5.137%	$56.6688	$56.67	$56.65	$56.70
Purchase #5	$215.48	9.311%	$235.5433	$235.54	$235.55	$235.50
Purchase #6	$44.77	8.598%	$48.6193	$48.62	$48.60	$48.60
Purchase #7	$188.40	6.601%	$200.8363	$200.84	$200.85	$200.80
7 purchase totals =	$924.88		$994.5435	$994.55	$994.50	$994.40