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	$96.70	3.424%	$100.011	$100.01	$100.00	$100.00
Purchase #2	$53.45	6.322%	$56.8291	$56.83	$56.85	$56.80
Purchase #3	$196.51	4.623%	$205.5947	$205.59	$205.60	$205.60
Purchase #4	$227.39	6.827%	$242.9139	$242.91	$242.90	$242.90
Purchase #5	$222.72	7.771%	$240.0276	$240.03	$240.05	$240.00
Purchase #6	$104.42	6.182%	$110.8752	$110.88	$110.90	$110.90
Purchase #7	$202.96	11.654%	$226.613	$226.61	$226.60	$226.60
7 purchase totals =	$1,104.15		$1,182.8645	$1,182.86	$1,182.90	$1,182.80