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	$168.64	6.621%	$179.8057	$179.81	$179.80	$179.80
Purchase #2	$160.52	13.321%	$181.9029	$181.90	$181.90	$181.90
Purchase #3	$43.57	4.801%	$45.6618	$45.66	$45.65	$45.70
Purchase #4	$106.31	5.267%	$111.9093	$111.91	$111.90	$111.90
Purchase #5	$162.38	13.727%	$184.6699	$184.67	$184.65	$184.70
Purchase #6	$164.52	10.792%	$182.275	$182.28	$182.30	$182.30
Purchase #7	$176.60	6.267%	$187.6675	$187.67	$187.65	$187.70
7 purchase totals =	$982.54		$1,073.8921	$1,073.90	$1,073.85	$1,074.00