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	$229.28	3.856%	$238.121	$238.12	$238.10	$238.10
Purchase #2	$178.84	10.796%	$198.1476	$198.15	$198.15	$198.10
Purchase #3	$56.56	11.106%	$62.8416	$62.84	$62.85	$62.80
Purchase #4	$139.42	12.408%	$156.7192	$156.72	$156.70	$156.70
Purchase #5	$202.44	4.455%	$211.4587	$211.46	$211.45	$211.50
Purchase #6	$211.77	6.515%	$225.5668	$225.57	$225.55	$225.60
Purchase #7	$190.28	13.224%	$215.4426	$215.44	$215.45	$215.40
7 purchase totals =	$1,208.59		$1,308.2975	$1,308.30	$1,308.25	$1,308.20