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	$50.82	5.834%	$53.7848	$53.78	$53.80	$53.80
Purchase #2	$163.27	4.111%	$169.982	$169.98	$170.00	$170.00
Purchase #3	$82.98	8.303%	$89.8698	$89.87	$89.85	$89.90
Purchase #4	$127.36	11.470%	$141.9682	$141.97	$141.95	$142.00
Purchase #5	$188.64	6.329%	$200.579	$200.58	$200.60	$200.60
Purchase #6	$206.48	11.749%	$230.7393	$230.74	$230.75	$230.70
Purchase #7	$202.38	10.833%	$224.3038	$224.30	$224.30	$224.30
7 purchase totals =	$1,021.93		$1,111.2269	$1,111.22	$1,111.25	$1,111.30