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	$205.87	3.572%	$213.2237	$213.22	$213.20	$213.20
Purchase #2	$54.32	12.823%	$61.2855	$61.29	$61.30	$61.30
Purchase #3	$81.39	6.774%	$86.9034	$86.90	$86.90	$86.90
Purchase #4	$205.83	11.588%	$229.6816	$229.68	$229.70	$229.70
Purchase #5	$137.41	3.792%	$142.6206	$142.62	$142.60	$142.60
Purchase #6	$238.41	6.810%	$254.6457	$254.65	$254.65	$254.60
Purchase #7	$206.96	12.871%	$233.5978	$233.60	$233.60	$233.60
7 purchase totals =	$1,130.19		$1,221.9583	$1,221.96	$1,221.95	$1,221.90