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	$189.27	4.691%	$198.1487	$198.15	$198.15	$198.10
Purchase #2	$130.45	13.611%	$148.2055	$148.21	$148.20	$148.20
Purchase #3	$35.75	10.860%	$39.6325	$39.63	$39.65	$39.60
Purchase #4	$180.77	13.632%	$205.4126	$205.41	$205.40	$205.40
Purchase #5	$107.86	3.289%	$111.4075	$111.41	$111.40	$111.40
Purchase #6	$148.63	3.270%	$153.4902	$153.49	$153.50	$153.50
Purchase #7	$178.35	11.237%	$198.3912	$198.39	$198.40	$198.40
7 purchase totals =	$971.08		$1,054.6882	$1,054.69	$1,054.70	$1,054.60