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	$70.58	4.460%	$73.7279	$73.73	$73.75	$73.70
Purchase #2	$37.57	7.294%	$40.3104	$40.31	$40.30	$40.30
Purchase #3	$145.95	6.870%	$155.9768	$155.98	$156.00	$156.00
Purchase #4	$187.40	13.789%	$213.2406	$213.24	$213.25	$213.20
Purchase #5	$236.57	10.857%	$262.2544	$262.25	$262.25	$262.30
Purchase #6	$98.39	4.272%	$102.5932	$102.59	$102.60	$102.60
Purchase #7	$141.68	8.798%	$154.145	$154.15	$154.15	$154.10
7 purchase totals =	$918.14		$1,002.2483	$1,002.25	$1,002.30	$1,002.20