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	$220.58	6.319%	$234.5185	$234.52	$234.50	$234.50
Purchase #2	$196.31	6.566%	$209.1997	$209.20	$209.20	$209.20
Purchase #3	$107.49	3.752%	$111.523	$111.52	$111.50	$111.50
Purchase #4	$42.42	5.221%	$44.6347	$44.63	$44.65	$44.60
Purchase #5	$203.95	9.607%	$223.5435	$223.54	$223.55	$223.50
Purchase #6	$166.66	4.441%	$174.0614	$174.06	$174.05	$174.10
Purchase #7	$123.85	8.637%	$134.5469	$134.55	$134.55	$134.50
7 purchase totals =	$1,061.26		$1,132.0277	$1,132.02	$1,132.00	$1,131.90