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	$186.95	11.517%	$208.481	$208.48	$208.50	$208.50
Purchase #2	$209.75	6.304%	$222.9726	$222.97	$222.95	$223.00
Purchase #3	$158.59	5.269%	$166.9461	$166.95	$166.95	$166.90
Purchase #4	$110.32	6.287%	$117.2558	$117.26	$117.25	$117.30
Purchase #5	$208.25	7.328%	$223.5106	$223.51	$223.50	$223.50
Purchase #6	$68.86	6.471%	$73.3159	$73.32	$73.30	$73.30
Purchase #7	$73.77	7.834%	$79.5491	$79.55	$79.55	$79.50
7 purchase totals =	$1,016.49		$1,092.0311	$1,092.04	$1,092.00	$1,092.00