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	$87.44	5.310%	$92.0831	$92.08	$92.10	$92.10
Purchase #2	$73.55	6.840%	$78.5808	$78.58	$78.60	$78.60
Purchase #3	$234.85	9.102%	$256.226	$256.23	$256.25	$256.20
Purchase #4	$160.40	7.169%	$171.8991	$171.90	$171.90	$171.90
Purchase #5	$247.47	11.552%	$276.0577	$276.06	$276.05	$276.10
Purchase #6	$6.73	13.824%	$7.6604	$7.66	$7.65	$7.70
Purchase #7	$205.91	10.444%	$227.4152	$227.42	$227.40	$227.40
7 purchase totals =	$1,016.35		$1,109.9223	$1,109.93	$1,109.95	$1,110.00