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	$201.96	3.864%	$209.7637	$209.76	$209.75	$209.80
Purchase #2	$6.26	13.170%	$7.0844	$7.08	$7.10	$7.10
Purchase #3	$130.91	8.565%	$142.1224	$142.12	$142.10	$142.10
Purchase #4	$166.39	4.341%	$173.613	$173.61	$173.60	$173.60
Purchase #5	$38.49	5.786%	$40.717	$40.72	$40.70	$40.70
Purchase #6	$226.38	13.289%	$256.4636	$256.46	$256.45	$256.50
Purchase #7	$27.52	3.741%	$28.5495	$28.55	$28.55	$28.50
7 purchase totals =	$797.91		$858.3136	$858.30	$858.25	$858.30