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	$116.49	10.362%	$128.5607	$128.56	$128.55	$128.60
Purchase #2	$182.72	7.657%	$196.7109	$196.71	$196.70	$196.70
Purchase #3	$202.46	4.814%	$212.2064	$212.21	$212.20	$212.20
Purchase #4	$130.61	13.377%	$148.0817	$148.08	$148.10	$148.10
Purchase #5	$157.93	6.743%	$168.5792	$168.58	$168.60	$168.60
Purchase #6	$45.40	8.169%	$49.1087	$49.11	$49.10	$49.10
Purchase #7	$189.95	5.588%	$200.5644	$200.56	$200.55	$200.60
7 purchase totals =	$1,025.56		$1,103.8120	$1,103.81	$1,103.80	$1,103.90