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	$240.30	9.765%	$263.7653	$263.77	$263.75	$263.80
Purchase #2	$69.93	13.414%	$79.3104	$79.31	$79.30	$79.30
Purchase #3	$40.45	11.497%	$45.1005	$45.10	$45.10	$45.10
Purchase #4	$233.40	9.660%	$255.9464	$255.95	$255.95	$255.90
Purchase #5	$186.69	12.813%	$210.6106	$210.61	$210.60	$210.60
Purchase #6	$55.34	9.233%	$60.4495	$60.45	$60.45	$60.40
Purchase #7	$152.46	12.544%	$171.5846	$171.58	$171.60	$171.60
7 purchase totals =	$978.57		$1,086.7673	$1,086.77	$1,086.75	$1,086.70