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	$125.33	13.772%	$142.5904	$142.59	$142.60	$142.60
Purchase #2	$31.38	8.680%	$34.1038	$34.10	$34.10	$34.10
Purchase #3	$53.44	7.377%	$57.3823	$57.38	$57.40	$57.40
Purchase #4	$240.25	3.156%	$247.8323	$247.83	$247.85	$247.80
Purchase #5	$141.54	8.737%	$153.9063	$153.91	$153.90	$153.90
Purchase #6	$91.59	13.425%	$103.886	$103.89	$103.90	$103.90
Purchase #7	$243.70	10.636%	$269.6199	$269.62	$269.60	$269.60
7 purchase totals =	$927.23		$1,009.3210	$1,009.32	$1,009.35	$1,009.30