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	$74.29	10.300%	$81.9419	$81.94	$81.95	$81.90
Purchase #2	$103.58	5.502%	$109.279	$109.28	$109.30	$109.30
Purchase #3	$36.63	11.846%	$40.9692	$40.97	$40.95	$41.00
Purchase #4	$200.76	3.352%	$207.4895	$207.49	$207.50	$207.50
Purchase #5	$176.95	13.229%	$200.3587	$200.36	$200.35	$200.40
Purchase #6	$96.31	6.449%	$102.521	$102.52	$102.50	$102.50
Purchase #7	$152.89	10.395%	$168.7829	$168.78	$168.80	$168.80
7 purchase totals =	$841.41		$911.3422	$911.34	$911.35	$911.40