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	$12.79	5.758%	$13.5264	$13.53	$13.55	$13.50
Purchase #2	$178.44	3.284%	$184.3	$184.30	$184.30	$184.30
Purchase #3	$249.29	6.122%	$264.5515	$264.55	$264.55	$264.60
Purchase #4	$245.73	5.844%	$260.0905	$260.09	$260.10	$260.10
Purchase #5	$240.63	12.116%	$269.7847	$269.78	$269.80	$269.80
Purchase #6	$152.27	12.744%	$171.6753	$171.68	$171.70	$171.70
Purchase #7	$174.97	12.505%	$196.85	$196.85	$196.85	$196.90
7 purchase totals =	$1,254.12		$1,360.7784	$1,360.78	$1,360.85	$1,360.90