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	$135.30	5.413%	$142.6238	$142.62	$142.60	$142.60
Purchase #2	$145.94	10.272%	$160.931	$160.93	$160.95	$160.90
Purchase #3	$233.95	9.303%	$255.7144	$255.71	$255.70	$255.70
Purchase #4	$54.42	4.647%	$56.9489	$56.95	$56.95	$56.90
Purchase #5	$182.54	9.865%	$200.5476	$200.55	$200.55	$200.50
Purchase #6	$114.62	3.593%	$118.7383	$118.74	$118.75	$118.70
Purchase #7	$114.57	7.744%	$123.4423	$123.44	$123.45	$123.40
7 purchase totals =	$981.34		$1,058.9463	$1,058.94	$1,058.95	$1,058.70