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	$198.26	12.227%	$222.5013	$222.50	$222.50	$222.50
Purchase #2	$64.62	12.758%	$72.8642	$72.86	$72.85	$72.90
Purchase #3	$17.56	6.190%	$18.647	$18.65	$18.65	$18.60
Purchase #4	$175.39	7.767%	$189.0125	$189.01	$189.00	$189.00
Purchase #5	$219.26	3.302%	$226.5	$226.50	$226.50	$226.50
Purchase #6	$115.91	6.668%	$123.6389	$123.64	$123.65	$123.60
Purchase #7	$70.98	7.819%	$76.5299	$76.53	$76.55	$76.50
7 purchase totals =	$861.98		$929.6938	$929.69	$929.70	$929.60