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	$167.59	10.827%	$185.735	$185.74	$185.75	$185.70
Purchase #2	$230.41	6.264%	$244.8429	$244.84	$244.85	$244.80
Purchase #3	$187.83	6.608%	$200.2418	$200.24	$200.25	$200.20
Purchase #4	$37.68	6.803%	$40.2434	$40.24	$40.25	$40.20
Purchase #5	$160.45	4.214%	$167.2114	$167.21	$167.20	$167.20
Purchase #6	$128.62	10.855%	$142.5817	$142.58	$142.60	$142.60
Purchase #7	$246.96	3.418%	$255.4011	$255.40	$255.40	$255.40
7 purchase totals =	$1,159.54		$1,236.2573	$1,236.25	$1,236.30	$1,236.10