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	$55.59	10.310%	$61.3213	$61.32	$61.30	$61.30
Purchase #2	$141.39	10.579%	$156.3476	$156.35	$156.35	$156.30
Purchase #3	$230.62	5.535%	$243.3848	$243.38	$243.40	$243.40
Purchase #4	$81.25	6.451%	$86.4914	$86.49	$86.50	$86.50
Purchase #5	$187.97	10.431%	$207.5772	$207.58	$207.60	$207.60
Purchase #6	$157.75	5.264%	$166.054	$166.05	$166.05	$166.10
Purchase #7	$174.48	8.823%	$189.8744	$189.87	$189.85	$189.90
7 purchase totals =	$1,029.05		$1,111.0507	$1,111.04	$1,111.05	$1,111.10